The 2024 Senate Map Is Terrifying for Democrats. That's One Reason Georgia's Runoff Matters.

Andrew Prokop / Vox
The 2024 Senate Map Is Terrifying for Democrats. That's One Reason Georgia's Runoff Matters. Sen. Raphael Warnock takes a selfie with a supporter during a campaign rally at Georgia Tech in Atlanta on November 18, 2022. (photo: Brandon Bell/Getty Images)

Democrats will have the majority next year. After that, things get much tougher.

Democrats prevailed in this year’s Senate elections — but that was the easy part.

The hard part is coming in 2024, when the party faces a starkly unfavorable map that could put them in a deep Senate hole for some time if things go even somewhat poorly.

So even though next week’s runoff pitting Sen. Raphael Warnock (D-GA) against Herschel Walker (R) won’t determine next year’s Senate majority, because Democrats have already won it, its outcome will have significant implications for how well-positioned the party is in its next very challenging Senate cycle.

Currently, just three Democratic senators represent states Donald Trump won in 2020, and they’re all up for reelection in 2024. These are Joe Manchin (D-WV), Jon Tester (D-MT), and Sherrod Brown (D-OH), though only Brown has confirmed he’s running again. 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 in the presidential contest where Republicans are defending seats are Florida and Texas — two states where Democrats keep coming up short of late. Democrats are also defending seats in five states Joe Biden very narrowly won in 2020. These seats are held by Kyrsten Sinema (D-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 just defied the naysayers in the tough year of 2022, winning at least one statewide contest in each of these — 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. Next year, there will be either five or six (depending on whether Walker can unseat Warnock in Georgia’s runoff election). The Senate has sorted by partisanship.

Of course, very close states at the presidential contest 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 and Joe Biden both won in Maine.

In 2024, all three Democratic senators representing states Trump won in 2020 — Manchin in West Virginia, Tester in Montana, and Brown in Ohio — are up.

Manchin and Tester haven’t announced whether they’re running again. Both have repeatedly won in their respective states, though their victories in 2018 were narrow (they each won by about 3.5 percentage points). If either or both retire, Democrats would have immense difficulty finding nominees with comparable cross-partisan appeal. Brown has said he is running again, and Ohio isn’t quite as red as the other two states, but if Republicans can find a competent challenger, he’ll face a tough contest too.

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 has infuriated progressives and may face a primary challenge from Rep. Ruben Gallego. In Nevada, Jacky Rosen just saw her colleague Catherine Cortez Masto narrowly survive a very close contest in 2022. Then there are the well-liked Rust Belt incumbents Debbie Stabenow, Tammy Baldwin, and Bob Casey Jr.

None of them will start off as underdogs, and all could well survive. But again, much will likely depend on the presidential contest, and if that contest trends toward the GOP, several of these Senate seats could follow.

Next is a set of likely Democratic states — Maine, where independent Sen. Angus King caucuses with the Democrats; he is 78 and hasn’t announced whether he’s running again, Minnesota (Amy Klobuchar), Virginia (Tim Kaine), and New Mexico (Martin Heinrich). All start as the favorites, but these states aren’t so overwhelmingly Democratic that they’re absolutely certain to win.

Beyond that, Democrats will also have to defend the seat of Sen. Bob Menendez (D-NJ), who is under federal investigation again. Menendez was previously indicted on public corruption charges in 2015, but his trial ended with a hung jury and the Justice Department gave up on the case. New Jersey is a solidly Democratic state but the party would probably feel better if their nominee wasn’t perennially a DOJ target.

Meanwhile, of the GOP-held seats up for election, only those held by Sens. Rick Scott (R-FL) and Ted Cruz (R-TX) are in remotely close presidential states.

Florida has been trending away from Democrats, as recently seen in Gov. Ron DeSantis and Sen. Marco Rubio’s landslide reelection victories this month. Texas has been trending toward Democrats (Trump only won it by 5.6 percentage points in 2020, and Cruz won reelection by 2.6 percentage points in 2018), but still, Democrats haven’t won a statewide race there since 1994.

The takeaway

Democrats’ forbidding 2024 Senate math raises the stakes of the Warnock/Walker runoff in Georgia — if the party starts off with a 51-49 majority rather than a 50-50 one, they can at least afford to lose one seat next cycle without losing control.

That’s especially important because, in a presidential year, the party’s biggest challenge will be holding on to their three seats in deep red states — West Virginia, Montana, and Ohio. The first big question is whether Manchin and Tester will run again, and if they do, the next question is whether they can keep defying partisan gravity, as Collins did in 2020.

But an analysis based purely on statewide partisanship would suggest Democrats are likely to lose all three seats even in a great year for their presidential candidate and their party nationally. That’s the main reason holding the Senate will be so tough for them. The 2022 Senate map was, as I wrote last year, “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.

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