Analysis: Senate tilting red, House blue for 2024

The possibility of a split congressional decision in 2024, with the Senate flipping to Republicans and the House turning over to Democrats, is looking increasingly likely.

Why it matters: By pursuing an impeachment inquiry into President Biden, House GOP leaders are making life awfully tough for their 18 vulnerable Republicans representing Biden 2020 districts. Threats of a government shutdown from GOP hardliners don't help either.

• Meanwhile, Biden's persistently low approval ratings are making it very difficult for red-state senators vying for re-election — West Virginia's Joe Manchin, Montana's Jon Tester and Ohio's Sherrod Brown — to win enough split-ticket voters at a time of record polarization.

By the numbers: To win back control of the Senate, Republicans only need to net two seats (one if the GOP presidential nominee prevails).

• The 2024 Senate map is historically favorable for Republicans: Republicans are aggressively contesting at least eight Democratic-held seats with Democrats hoping — in a best-case scenario — of putting Sen. Ted Cruz's Texas seat in play.
• But House Republicans are in an equally precarious position. To win back control of the House, Democrats only need to flip a net five seats. A new House race analysis from Inside Elections (subscription) rates 11 seats as toss-ups — seven held by Republicans, and four by Democrats.

The big picture: With national polarization near all-time highs, most voters are casting straight-party ballots.

• There are only five senators representing states carried by the opposing party's presidential candidate. Of those, the only ones up for re-election in 2024 are the three vulnerable Democratic senators mentioned above.
• There are currently only 23 lawmakers (18 Republicans, 5 Democrats) representing House districts carried by the presidential candidate from the opposite party.
• That means House Republicans face a whole lot more exposure than Democrats unless their swing-district members can create ample distance from their party's leadership.
• Nine of the 18 Biden-district Republicans are freshmen who outperformed Trump by at least five points in last year's election. As a sitting lawmaker, convincing voters of your independence is more difficult when you have a voting record in Congress — especially with the higher turnout of a presidential election year.

Between the lines: House GOP and Senate Democratic leaders are employing two strategies to protect their most vulnerable members.

• House GOP leaders have encouraged unity within their conference, with Speaker Kevin McCarthy (R-Calif.) trying — often awkwardly — to find a middle ground that can satisfy both the pragmatists and the hardliners.
• It's notable that politically vulnerable House Republicans haven't spoken out against the pursuit of an impeachment inquiry against Biden, even though they'll need to win over Biden voters to secure re-election.
• By contrast, Senate Majority Leader Chuck Schumer (D-N.Y.) is content to let his red-state senators demonstrate some independence from the White House (at least in an election year). Manchin is openly feuding with Biden, while Tester joined with Republicans on a vote to roll back an ESG rule — prompting Biden's first veto.

Reality check: Candidates still matter, despite the surge in partisan voting behavior.

• The reason Senate Republicans have been active in endorsing preferred candidates against Manchin and Tester is that they recognize those Democrats have a track record in winning crossover votes — typically because of weak GOP challengers in the past.
• House Democrats are also facing recruitment questions in several battleground districts where the leading candidates are to the left of a typical swing voter — and where crowded primaries could get messy.

• House Republicans have a few recruitment challenges of their own against a handful of the Democrats representing Trump districts, where the losing GOP candidate from 2022 is seeking a rematch.

Driving the news: House Democrats have been getting favorable news on the redistricting front, with court decisions boosting their chances of picking up a seat in three Southern states: Alabama, Florida and Louisiana.

• Democrats also have a reasonable chance of netting several additional seats if New York is ordered to redraw its congressional lines for 2024. The case will be decided later this year.
• On the flip side, Republicans are expected to gain several seats from North Carolina's GOP-controlled redistricting.

Zoom in: Republicans and Democrats are tied on the congressional generic ballot at 44%, according to RealClearPolitics' polling average, with polls showing both parties are viewed unfavorably by most voters.

• Biden and Trump are also virtually tied — Trump at 45.6%, Biden at 45% — in the RCP polling average.

The bottom line: The country is deeply divided, which foreshadows the likelihood of split government continuing past next year.

• Political sentiment has remained remarkably stable over the last year — even in light of major political developments, like Trump's indictments. That's unlikely to change heading into 2024.
• All politics is now national. That makes the fundamentals as significant as ever: A favorable map gives Senate Republicans an early edge, and House Democrats a slight advantage. The battle for the presidency, meanwhile, looks like a pure toss-up.
• But if Biden, Trump (or any GOP opponent) pulls away in the presidential race, there's a good chance they'll hand their party the House majority as well.

Editor's note: This story has been corrected to remove a reference to Tester voting against Biden's Labor nominee.