Democrats Playing Defense: The 10 Senate Seats Most Likely to Flip in 2024

The 2024 election is still more than a year away, but Senate races across the country are already well underway. Democrats enter 2024 with a 51-49 seat majority, which means that if Republicans win the presidential election, one GOP pickup in the Senate flips the balance of power to Republicans. Democrats can only afford to lose one seat if they keep the presidency, and none if they lose it. Following the Republican party’s poor performance in the 2022 midterms, Senator Steve Daines (R-MT) replaced Sen. Rick Scott (R-FL) as the chair of the National Republican Senatorial Committee (NRSC). While Daines has a plethora of targets, Republicans will be up against experienced Senators who are used to winning in red states. There are three factors that play a pivotal role in every race: President Biden’s approval and the national environment, how much sway the NRSC has in primaries, and the advantages of incumbency - positive name recognition, no primaries, experience winning, and early fundraising. Here are the 10 Senate seats most likely to flip:

1. West Virginia (Incumbent Sen. Joe Manchin is a Democrat)

West Virginia will likely remain at #1 on this list for the entire election cycle. Sen. Joe Manchin won here by 3.2 percentage points in 2018 and fell just short of 50% of the vote. 2024 is shaping up to be less favorable for Democrats than the 2018 blue wave year, and Manchin will likely face Governor Jim Justice, who won by more than 33% in 2020, in a state that former President Trump won by almost 40 points in 2020. These factors are leading Manchin to flirt with a bid for the White House, but if the moderate Democrat chooses to run for President, there is no Democrat in West Virginia that stands a chance at keeping that seat blue this year.

How Manchin wins: Manchin has consistently been on the ballot in West Virginia since 2004 and has won every statewide office for which he has run. Add the trust and recognition among West Virginian voters to his tendency and fearlessness to oppose President Biden and congressional Democrats, and he could win another term by touting his moderateness and popularity in his state. And, if Rep. Alex Mooney upsets Justice in the Republican primary, Manchin’s chances of victory increase dramatically.

How Manchin loses: Justice is a very popular Republican in a state that voted overwhelmingly for Trump twice. Increasing partisan polarization only helps his chances of victory, and Justice defeats Manchin in recent polls. West Virginia Republicans have the massive advantage of the GOP Presidential nominee winning by around 40 points, which helps them in the Senate race. 

2. Montana (Incumbent Sen. Jon Tester is a Democrat)

Unlike Manchin, Sen. Jon Tester has already begun his reelection campaign for the Senate seat he has held since he flipped it from red to blue in 2006. However, Tester may be fighting his toughest battle yet. Trump won Montana by 16 points in the 2020 election, and Sen. Daines defeated then-Governor Steve Bullock (D) to win reelection to the Senate by 10 points. Tester touts his farming and teaching background and his moderate record to appeal to Montana’s rural farmers, who usually vote for the GOP. Tester will likely face either Tim Sheehy - a businessman and former Navy SEAL - or Rep. Matt Rosendale - the hard-right congressman from western Montana who lost to Tester in 2018. While Rosendale has indicated that he would run, Sheehy has already announced his candidacy. National Republicans have made it abundantly clear that they think Sheehy will have a better chance of defeating Tester - Sheehy received endorsements from 11 Senators, including Daines and Sen. John Thune, the Minority Whip (second most powerful Republican, behind Sen. Mitch McConnell), Montana Governor Greg Gianforte, and Rep. Ryan Zinke (R-MT). Despite Sheehy’s endorsements, Rosendale defeated Sheehy 64%-10% in the latest primary poll, with 26% of Montana Republicans undecided. However, Rosendale has not announced his candidacy yet, likely because Trump told the Congressman that he would not receive the ever-so-coveted Trump endorsement. Polling suggests that Rosendale could win the nomination without the Trump endorsement. Still, if Rosendale chooses not to run, Tester will have to defeat a more moderate but inexperienced Sheehy.

How Tester wins: Tester defeated Rosendale in 2018 by 3.6 points, and a Rosendale rematch is possible. If Tester’s moderate appeal and Montana background can overcome increasing polarization and appeal to the Republican voters that will vote Republican everywhere else on the ballot, he may be on track for reelection. If Tester faces Sheehy, Tester will have the advantage of being known and trusted by Montana voters and has to build off that.

How Tester loses: Like West Virginia, Montana consistently votes for Republicans by double digits. Republicans will likely win Montana in the presidential and governors race, which are huge potholes in Tester’s road to victory. If Rosendale can rally the same support that propelled him to Montana’s at-large House seat in 2020 and sufficiently tie Tester to Biden’s unpopularity in Montana, he has a good chance. If Sheehy wins the nomination, he will have to win the backing of Rosendale voters in the general election and build off of Republican victories in Montana in the Presidential, Governor, and House elections.

3. Ohio (Incumbent Sen. Sherrod Brown is a Democrat)

Sen. Sherrod Brown is the last of the three Senate Democrats running for reelection in states that Trump won twice. Trump won Ohio by 8 points in 2020, Sen. J. D. Vance won by 6.1 points in 2022, on the same ticket which Governor Mike DeWine (R) won reelection by a landslide 25 points. In 2018, DeWine won by less than 4 points, and Brown won by 6.8 points. These elections have solidified Ohio as a reliable Republican state. Ohio's Obama-era competitiveness has rapidly faded - every statewide elected official besides Brown is a Republican. Brown could face any of three Republicans: Bernie Moreno, Matt Dolan, or Frank LaRose. LaRose is Ohio’s Secretary of State, and Moreno and Dolan can self-fund their campaigns. Dolan placed third in the Republican primary in the 2022 Senate race, while Moreno dropped out and endorsed Vance. The Trump endorsement will likely have a significant role in who wins the primary, which all three candidates are chasing. Moreno already secured Vance’s endorsement, and LaRose prides himself on receiving Trump’s endorsement in the 2022 race for Secretary of State. Polling indicates that most Republican voters are undecided, but LaRose has performed best among the three candidates. Meanwhile, Brown is busy selling himself as a moderate Democrat who works across the aisle. Brown and Vance introduced the Rail Safety Act of 2024 after the Norfolk Southern train derailment in Ohio. Brown’s messaging centers on bringing jobs back to Ohio and working for workers. Based on the 2016 and 2020 elections, Brown will have to outperform Biden by 8 points.

How Brown wins: Brown’s past three victories in this Senate election demonstrate that Ohio voters like and trust him. He outperformed DeWine’s Democratic opponent in 2018 by 7 points, polls well (so far), and is a strong fundraiser. If his bipartisan and pro-worker messaging continues to resonate with the Ohio electorate, Brown can outperform Biden and win reelection.

How Brown loses: If the Republican nominee avoids controversy, does a good enough job of tying Brown to Biden, and builds off the Trump endorsement, Brown becomes more vulnerable than he already is. Moreover, if the Presidential ballot is a rematch of 2020, Brown may have difficulties distancing himself from Biden and convincing voters to split their ticket.

4. Arizona (Sen. Kyrsten Simena is an Independent who caucuses with Democrats)

Sen. Kyrsten Sinema will lose her seat this fall, but who replaces her is up for the taking. Rep. Ruben Gallego will most likely be the Democratic nominee, but the Republican primary could get very intense: Kari Lake, the 2022 GOP nominee for Governor, who lost by less than 1 point, has expressed interest in running for Senate and indicated that an announcement would come in the fall. Lake’s polarizing figure does not poll well against Gallego, but if Sinema runs as an Independent, the ensuing three-way race could see Gallego hampered by the spoiler effect. Moreover, Arizona is still a swing state - Biden only won by 0.31 points in a good year for Republicans. The GOP nominee could win over 50% of the vote, regardless of whether Sinema is in or out. Although Sinema has not announced her candidacy, Arizona is high on this list because of the potential for a swing state to have a three-way race.

How Democrats (Gallego) win: Gallego has performed very well in recent polls, including polls of a three-way race. If Gallego can harness Arizona’s Democratic trend, continue to outraise Simena, and win moderate Democrat voters, he is in a good position to become Arizona’s next Senator. Of course, his chances of victory skyrocket if Sinema chooses not to run, as there will not be a spoiler effect to ruin his chances. Gallego will probably do better if Lake is the GOP nominee, but he should not bank on it.

How Republicans win: If Republicans nominate a less polarizing candidate than Kari Lake, they will be in a great position to watch Sinema drag Gallego’s numbers down and emerge victorious in a three-way race. Nominating Lake may result in moderate Republicans backing Sinema, giving Gallego a better chance to win. If Sinema chooses not to run, Republicans must have a strong candidate and a good year to flip Arizona.

5. Nevada (Incumbent Sen. Jacky Rosen is a Democrat)

In 2018, then-Rep. Jacky Rosen was one of two Democrats to flip a Senate seat, defeating incumbent Senator Dean Heller by 5 points. 2024 will be a close race - Rosen’s 2018 margin of victory is still the highest margin of victory in Nevada since 2014, and she had the benefit of the 2018 blue wave. Barring something shocking in the primary, Rosen will face one of two candidates in the general election: Jim Marchant or Sam Brown. Nevada’s Republican primary may bear a striking resemblance to Montana’s: an NRSC-picked conservative with less political experience challenging a more extreme candidate who has won statewide primaries but is more likely to lose the general election. Brown will have to win a primary, something he is yet to accomplish. Despite the backing of Washington’s Republicans, Marchant won a primary last year and is likely to win over the Trump wing of the party. If Jim Marchant’s name rings a bell, it is not just because he was the Republican nominee for Nevada’s Secretary of State in 2022 but also because he was directly involved in trying to overturn the results of the 2020 election. Marchant stated that, if elected, he would not certify a Biden victory in Nevada in 2024, and he repeated the false claim that Biden did not win Nevada in 2020. In 2022, Democrats made democracy a critical piece of campaign messaging, and Marchant was one of many election-denying Republican nominees for Secretary of State that lost in November. Democrat’s democracy message resonated with Nevada voters when nothing else did. Joe Lombardo said that Biden won Nevada and the 2020 election and proceeded to win the Governor’s race by 1.5 points, flipping the seat. However, election-denying candidates like Marchant and Adam Laxalt lost extremely close races. All three of those candidates are pro-life, so the most significant difference was what they thought of the 2020 election, and the election deniers lost.

In 2018, Rosen defeated Heller by making Obamacare the central focus of her campaign. To counter that, Heller went on record saying that he would not vote to repeal Obamacare, citing the benefits of the law that were very popular in Nevada. However, when Senate Republicans forced a vote on a bill that repealed parts, but not all, of Obamacare, Heller voted for it. Rosen’s winning strategy was to take the popular side of a contentious and polarizing issue, and she can do that again in 2024.

How Rosen wins: Rosen defeated Heller on a single issue and had most of Nevada’s voters on her side. 2024 is shaping up to be the same - but with election denial instead of health care. 2022 proved that Nevada voters would not elect election-denying Republicans, and 2024 polling supports this claim: in the only poll of this race, conducted in May, Rosen defeats Merchant by 5 points. If Brown is the nominee, he will have to navigate the difficulties of a general election, which he has never reached. 

How Rosen loses: Never count Republicans out in Nevada. If Brown wins the nomination and focuses his campaign on the economy, crime, and his military background, he has a strong chance of beating Rosen, especially if Nevada voters disapprove of Biden and Rosen. To counter his inexperience, Brown will have the guidance and backing of the NRSC and the top Republican strategists to defeat Rosen. So far, he has proven himself to be a strong fundraiser, which brings him one step closer to bringing Republicans over the line in Nevada.

6. Michigan (Incumbent Sen. Debbie Stabenow is a retiring Democrat)

Sen. Debbie Stabenow is retiring, which opens up Michigan’s Senate seat. While Trump won Michigan in 2016, Democrats have fared quite well here in every election after that. Stabenow won by 6.5 points, and Gretchen Whitmer flipped the Governor election by 9.6 points in 2018. Sen. Gary Peters won by 1.7 in 2020, while Biden flipped Michigan blue by 2.8. Gov. Whitmer won reelection by 10.5 points in 2022, and Democrats won full control of the state government for the first time in 40 years. Although it is worth noting that the GOP nominee to take on Whitmer, Tudor Dixon, was polling in seventh place before the top five candidates were disqualified and the sixth was arrested. If Republicans had avoided the chaos, that race could have been closer. In 2022, voters also approved an amendment to the state Constitution to codify abortion access by 13.3 points. Michigan is shifting to the left, but its inherent nature as a swing state and an open race means that Republicans have a good chance at picking up a seat here. Rep. Elissa Slotkin is the frontrunner for the Democratic nomination, and Republicans hope that former Rep. Mike Rogers or New York Stock Exchange Vice Chair John Tuttle enters the race. Former Rep. Peter Meijer has expressed interest, but he is almost certain to lose the primary for his anti-Trump views. Despite 2022, Michigan is still a swing state, especially in a Presidential election year. While Slotkin enters the race as the favorite, Republicans can and likely will make this race competitive.

How Democrats win: Slotkin will most certainly win the primary, and she is well-positioned to build off Michigan’s 2022 blue wave. Democrats did not lose in Michigan in 2022, and Slotkin’s spot in the bipartisan Problem Solvers Caucus will help her appeal to moderate Democrats, Independents, and moderate Republicans. Slotkin has proven to be a strong fundraiser, and has experience winning in Michigan. 

How Democrats lose: If Republicans nominate a moderate that can appeal to independent voters in the same way Slotkin does, they could win back the voters that kept previous Michigan elections competitive and even winning for the GOP. With the exception of the 2022 Governor election, Michigan elections have been close, and they will continue to be close. In the right environment, a candidate with strong crossover appeal and fundraising numbers can win this open seat.

7. Wisconsin (Incumbent Sen. Tammy Baldwin is a Democrat)

Sen. Tammy Baldwin is a progressive Democrat running for a third term in a swing state that just narrowly reelected Republican Sen. Ron Johnson in 2022. Baldwin is less familiar with close elections - she won by 5.5 points in 2012 and nearly 11 in 2018. Republicans have two main hurdles - finding their candidate and Baldwin’s tendency to win big. When Republican Reps. Mike Gallagher, Brien Steil, and Tom Tiffany declined to run for Senate, the lack of strong Republican candidates in Wisconsin became apparent. Baldwin raised more than $3.2 million in the second quarter and Republicans have no declared candidates. Of the three Republicans who have expressed interest, two of them - Eric Hodver and Scott Mayer -  have no political experience and will be heavily reliant on self-funding their campaigns. The third, former Sheriff David Clarke, has much more unwanted baggage - his close ties to Trump and his views on abortion and conspiracy theories - that will probably push Independent voters toward Baldwin. All primary polling included Gallagher, but Clarke still had strong leads. Republicans will have to come back from Judge Janet Protasiewicz’s 11-point win over her Republican opponent in Wisconsin’s Supreme Court election in April of 2023, but they are confident that a stronger nominee will overcome that gap more easily.

How Baldwin wins: Baldwin is an excellent fundraiser with a strong connection with the Wisconsin electorate, evidenced by her 2012 and 2018 wins. Democrats will gladly watch a chaotic primary between relatively unknown and divisive candidates while fundraising and focusing on the general election (advantages of incumbency). Clarke’s rhetoric risks disinteresting Independents and some moderate Republicans, which increases Baldwin’s chances.

How Baldwin loses: Wisconsin is a swing state - both Trump in 2016 and Biden in 2020 won by less than 1 point. Although Republicans face an uphill battle, Republicans just won a Senate race in Wisconsin, and Trump lost by less than a point in 2020. Catching up in fundraising will be a necessary step to rallying the voters that reelected Johnson in 2022. Although flipping Baldwin’s seat will be tougher than defending Johnson’s, Wisconsin Republicans know how to win, have won before, and are capable of picking up a swing state Senate seat.

8. Pennsylvania (Incumbent Sen. Bob Casey is a Democrat)

Sen. Bob Casey is running for a fourth term in 2024. Casey won his previous elections by 17.4 points in 2006, 9.1 in 2012, and 13.1 in 2018. Unseating Casey will be very difficult, and Republicans are coming off a 4.9 point loss to John Fetterman in 2022. Nominating Dr. Oz hurt Republicans in the general election, and they have turned to Dave McCormick, the runner-up in the 2022 Republican primary. McCormick came very close to defeating Trump-endorsed Oz and was widely regarded as more electable in the general election. However, there are some very important differences between Pennsylvania’s 2022 Senate election and its 2024 Senate election. First, McCormick and Oz were running for an open seat previously held by Republicans, as opposed to unseating a three-term Senator in Bob Casey. Second, Fetterman had never actually ran a statewide election before his Senate bid - he was on the ticket as Gov. Tom Wolf’s Lt. Gov, not running an independent race. Accordingly, Pennsylvania voters were less familiar with Fetterman than they are with Casey. Third, McCormick veered to the right in the primary to get the Trump endorsement. He has nothing to show for it, and this makes him less appealing to independents and moderate Democrats in 2024. McCormick does have important factors in his favor - he has already secured Minority Leader Mitch McConnell’s endorsement, and Doug Mastriano is not running - Mastriano, the 2022 Republican nominee for Governor, beat McCormick in primary polls, despite his decisive loss at the hands of now-Gov. Josh Shapiro in 2022.

How Casey wins: Casey won his previous three elections by an average of 13.2 points. In 2006 and 2018, Casey ran in a midterm with a Republican president, but in 2012 he was on the same ticket as President Barack Obama and outran him by 3.7 points. Casey is an exceptionally strong candidate, raised $4 million(!) in the last quarter, and defeated McCormick by 12 points in the latest poll between the two, with 53% of the respondents saying they would vote to reelect Casey. The last time Casey was on the ballot in a Presidential election, he outran Obama by 3.7. If he outruns Biden by just 3 points, McCormick will have to outrun the Republican nominee (presumably Trump) by the same amount, which will not be easy.

How Casey loses: McCormick was much more electable than Dr. Oz and was perceived as more moderate. If McCormick can use that perception to attract swing voters without isolating the Trump base, which he can do, he has a chance of winning. McCormick is wealthy and can self-fund his campaign, but he also needs lots of individual small donors to demonstrate that he has the base in Pennsylvania to win. McCormick and Republicans should make the race competitive, and if Republicans play their cards right, get a good national environment, and a stroke of luck, Casey might not win a fourth term.

9. Texas (Incumbent Sen. Ted Cruz is a Republican)

In 2018, then-Rep. Beto O’Rourke came 2.3 points away from shocking the country and flipping Texas blue. O’Rourke visited every single one of Texas’s 254 counties, had the benefit of the blue wave, and raised $80 million, but could not overcome the partisan lean of Texas and Sen. Ted Cruz. In 2024, Democrat Rep. Colin Allred aims to pick up where O’Rourke left off and defeat Cruz. Allred polls 5-7 points behind Cruz, but national Democrats will pour loads of money into his campaign (they tend not to like Ted Cruz). Since 2018, Texas has trended back to the right. In 2020, Trump won by 5.6 points and Sen. John Cornyn won by 9.6 points. In 2022, Gov. Greg Abbott won reelection by nearly 11 points. Allred faces some primary challengers, most notably State Sen. Roland Gutierrez from Ulvalde, but Allred polls ahead of him. Gutierrez and Allred will (should) likely keep their focus on Cruz, not each other.

How Cruz wins: In 2018, O’Rourke threw everything at this race and had the right national environment but was still unable to overcome the partisan lean of Texas. 2024 is not shaping up to be the blue wave year that 2018 was, which plays to Cruz’s advantage. Even though Texas is closer than it has been in previous elections, Texas is still a red state, and this is Cruz’s race to lose.

How Cruz loses: National Democrats will pour money into Allred’s campaign, and he only needs to do marginally better than O’Rourke across the board. Allred will have to do everything O’Rourke did and more, but in the right environment, this race could become very competitive. Democrats will be motivated to pick up a seat and defeat Cruz. 

10. Florida (Incumbent Sen. Rick Scott is a Republican)

In 2018, then-Governor Rick Scott flipped this seat by the razor-thin margin of 0.12 points - the closest Senate election since 2008 (Minnesota’s 2008 Senate election was decided by 0.011 points, which was 312 votes). Since becoming a Senator, Scott chaired the NRSC in 2022, overseeing a Republican effort that wound up in losing one seat, becoming the first time since the 2002 midterms that the President’s party gained seats in the Senate. Following the election, Scott mounted an unsuccessful bid to be the Senate minority leader and was the subject of heavy criticism for suggesting that Social Security and Medicare should sunset every five years. While these opinions are generally unpopular, Florida has leaned further to the right in recent years, culminating in the 2022 midterms, when Gov. Ron DeSantis won by 19.4 points and Sen. Marco Rubio won by 16.4 points. Florida’s recent turn from the center to the right is leaving Democrats empty-handed - Republicans control the Governorship, both Senate seats, every single statewide office, and supermajorities in the state legislature. As a result, Democrats are scrambling to find a candidate with winning chances. 

How Scott wins: This is not the state that Scott won in 2010, 2014, or 2018. Florida’s rapid shift from a swing state to a red state will help Scott’s reelection bid. Even though his victories are often by thin margins, he is no stranger to winning Florida elections. Democrats do not have their candidate and are frantically trying to push back against the power of Florida Republicans. As of now, they do not have enough to take down Scott. Scott has a fundraising advantage, polling advantage, incumbency advantage, and partisan advantage. Countering all of those factors will be very difficult for Democrats.

How Scott loses: In all three of Scott’s elections, he has never won by more than 1.2 points. In 2010, Rubio won the Senate election by 19.2 points, while Scott won the corresponding election for Governor by only 1.1 points, so Scott has a history of underperforming other Republicans. Despite Florida’s Republican lean, Scott’s unpopular policy proposals received bipartisan backlash. If Democrats find a candidate that can corral the anti-Scott voters in previous elections, put Scott’s incredibly unpopular policy proposals in the limelight, and raise a lot of money, a good year for Democrats might yield a return to winning ways in the Sunshine State.

Summary

The biggest priority for Senate Democrats is to hold their current seats. Republicans can win a majority by winning the two of the three seats in the states Trump will likely win: West Virginia, Montana, and Ohio. Republicans will be confident in their ability to flip these seats, while Democrats trust their incumbents to continue to win elections in heavily-contested races. Only time will tell.

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Photo credit: https://www.cnn.com/2023/07/19/politics/trump-senate-races-2024/index.html