Sen. Joe Manchin (D-WV) will not run for reelection — a decision that likely means Democrats will lose a Senate seat in the narrowly divided chamber in 2024.
The stubborn centrist represented one of the most Republican states in the country — one that Trump won by nearly a 39 percentage point margin in 2020. Yet Manchin was able to defy West Virginia’s partisan leanings via his long history in state politics, including as a former governor, dating back to the years when Democrats won the state regularly.
Since then, the West Virginia Democratic Party has been decimated, as the state’s voters have increasingly voted with their national partisan loyalties. It is hard to believe any other potential Democratic nominee would be able to match Manchin’s political strength there.
Democrats currently have a 51-49 majority in the Senate, so losing Manchin’s seat would put them back to 50-50 — still enough for control if President Joe Biden and Vice President Kamala Harris win reelection.
The problem is that Democrats’ 2024 Senate challenges go far beyond West Virginia. They face such a starkly unfavorable map that, if things even go somewhat poorly for the party, they could fall into a deep Senate hole for years to come.
Besides Manchin, two other Democratic senators represent states Donald Trump won in 2020, and they’re also up for reelection in 2024. Sens. Jon Tester (D-MT) and Sherrod Brown (D-OH) are both running again, but these are all very red states, and winning them in a presidential year will be quite difficult for Democrats.
But the vulnerabilities go deeper. The only remotely close states (per presidential results) where Republicans are defending seats are Florida and Texas — two states where Democrats have had few victories in recent years. Meanwhile, Democrats are also defending seats in five states Joe Biden very narrowly won in 2020. These seats are currently held by Kyrsten Sinema (I-AZ), Tammy Baldwin (D-WI), Bob Casey Jr. (D-PA), Jacky Rosen (D-NV), and Debbie Stabenow (D-MI).
Democrats might think they have nothing to worry about regarding this group of seats, because, look, the party defied the naysayers in the tough year of 2022, winning at least one statewide contest in all these states — so clearly these states lean in their favor.
But it’s always a mistake to overread the results of the last election, and to underestimate how much things could change before the next one. Particularly if Trump is not the nominee again, the party coalitions could be scrambled in unpredictable ways. And even Trump came quite close to winning these states in 2020.
The Class of 2024
Senators serve six-year terms, so only one-third of the body is up for election each cycle. And the particular grouping of Senate seats (referred to as a “class”) up for election in 2024 has enjoyed a particularly charmed run for Democrats. You have to go all the way back to the 1994 GOP wave for a strong Republican performance. Since then, they’ve been on the ballot in the following years:
- 2000: A closely fought presidential year in which Al Gore won the popular vote but George W. Bush won the Electoral College, and Democrats picked up four Senate seats on net
- 2006: A Democratic wave year, in which the party retook both the House and the Senate, picking up six seats in the latter chamber
- 2012: A strong Democratic year for Barack Obama’s reelection, in which the party unexpectedly expanded its Senate majority by two seats
- 2018: Another Democratic wave year — but the party had won so many seats in deep red states in previous cycles that they had several incumbents in strongly Republican territory, so they ended up with a net loss of two seats
So this Senate class is risky for Democrats in part because they’ve had such good luck with it in the past. Nearly half of Democrats’ Senate majority — 23 sitting senators — come from this grouping of seats, so they’ll all be on the ballot in 2024. Meanwhile, only 10 Republicans will be up, though special elections could increase this number. That’s already a numerical disadvantage. But the disadvantage extends to which specific seats are up.
Which specific seats are up
To understand the extent of the Democrats’ challenge, it’s important to realize that the Senate has changed. In the past, it was common for a state’s voters to back Senate and presidential candidates from different parties. For instance, after the bitterly fought 2000 election, 30 of 100 sitting senators represented states that their party’s presidential nominee did not win in the most recent election. That’s a lot of ticket-splitting.
Since then, that number has gradually dwindled, as red-state Democrats and blue-state Republicans have retired or gone down to defeat. When Trump took office, there were 14 such senators remaining. Now, there are just five. The Senate has sorted by partisanship.
Of course, states that have a roughly equal partisan balance can still go either way. But it’s gotten much tougher to defy partisan gravity in deeply Republican or Democratic states — especially in a presidential year. In 2016, zero states elected presidential and Senate candidates from different parties. In 2020, just one state did, as Republican Sen. Susan Collins won in Maine, a Biden state.
Now, in 2024, the seats of all three Democratic senators representing states Trump won in 2020 — Manchin in West Virginia, Tester in Montana, and Brown in Ohio — are up.
Manchin’s seat is likely lost due to his retirement. But the best hope for Tester and Brown is for Republicans to have a messy and divisive primary, after which a controversial nominee emerges. Even then, though, it would be tough to defy the presidential lean of their states, which have both backed Trump pretty solidly in the past two cycles.
So that’s three seats where, per underlying partisanship alone, Democrats will have a hard go of it.
Then there are five swing states which, if recent history is any guide, are likely to have closely matched Senate and presidential outcomes.
In Arizona, Kyrsten Sinema quit the Democratic Party, and it’s currently unclear whether she’ll run for reelection; if she does, a three-way race would ensue. In Nevada, Jacky Rosen just saw her colleague Catherine Cortez Masto narrowly survive a very close contest in 2022. Then there are the three seats in the Rust Belt swing states — those held by Tammy Baldwin (D-WI) and Bob Casey Jr. (D-PA), who are running again, and Debbie Stabenow (D-MI), who is retiring.
Democrats don’t start off as underdogs in any of these states, and they could well win them all. But again, much will likely depend on the presidential contest. If that contest trends toward the GOP, several of these Senate seats could follow.
Moving on to the GOP-held seats up for election — barring some sort of GOP candidate catastrophe in a deep red state, Democrats have only two plausible targets: Florida and Texas.
In Florida, Sen. Rick Scott (R) is running for a second term. Back in 2018, Scott only won by an incredibly narrow 0.12 percent margin. But the Sunshine State has been trending away from Democrats since then, as seen in Gov. Ron DeSantis and Sen. Marco Rubio’s landslide reelection victories last year.
Texas, where Sen. Ted Cruz (R) is up, has been moving the other way demographically —Trump only won it by 5.6 percentage points in 2020, and Cruz won reelection by 2.6 percentage points in 2018). Still, Democrats haven’t won a statewide race there since 1994. Rep. Colin Allred, the frontrunner for the Democratic nomination to face Cruz, hopes to change that.
Democrats are fortunate that they picked up a Senate seat in the 2022 cycle, expanding their majority to 51-49 rather than 50-50. That gives them a cushion to survive the likely loss of Manchin’s seat. But they have no other room for error.
The problem is that even if Democrats have a great year nationally in 2024, the underlying partisanship of the map means they’d likely lose three seats. The 2022 Senate map was, as I wrote during that cycle, “relatively balanced,” but the 2024 map just isn’t. (And again, that’s mainly because Democrats have been so successful in these races previously, so they simply have more to lose.)
And if 2024 is not a good year for Democrats nationally? Well, then they could lose some or all of those five swing state seats, putting them at a serious deficit in the Senate that it could take many years to climb out of.
Update, November 9, 2023, 4:00 pm ET: This article was originally published in November 2022. It has been updated to include developments in Senate races since then.