The House and Senate could make history this election

Analysis by Harry Enten, CNN

(CNN) — Recent polling, including new surveys out Tuesday, shows that 2024 may produce something never seen before in American history: The House could flip from Republican to Democratic control, while the Senate may flip from Democratic to Republican control.

If that happened, it would be the first time in over 230 years of congressional elections that the two chambers of Congress changed partisan control in the opposite direction.

The possibility for this historic oddity arises in large part because the battleground maps for the narrowly divided House and Senate are totally different.

All 435 seats are up in the House. Democrats need a net pickup of just four seats to win a majority.

They could grab those four from New York alone. There were four House races in the Empire State that the GOP won by less than 5 points in 2022, all in districts that Joe Biden would have carried two years earlier under the current district lines. They include New York’s 4th District on Long Island, the 17th and 19th districts in the Hudson Valley, and the 22nd District in Central New York, which was decided by a point two years ago and where the lines have since been heavily redrawn to Democrats’ advantage.

The battle for the Senate is something else entirely.

Remember that only about a third of the chamber’s 100 seats are up every cycle. This year, a bunch of seats held by Democrats or those who caucus with them are on the ballot in red-leaning states.

The math for Republicans is simple: To win the Senate, they need a net pickup of either one seat (if the incoming vice president is a Republican) or two seats (if the incoming vice president is a Democrat).

Republicans seem fairly likely to flip at least two seats, thanks to red Montana (where Democratic Sen. Jon Tester is struggling) and very red West Virginia (where independent Sen. Joe Manchin is retiring). Republicans also have a clear opportunity to unseat Democratic Sen. Sherrod Brown in Ohio, which Donald Trump won twice and will likely do so again.

The GOP has further pickup opportunities in four states that Trump carried in 2016: Arizona, Michigan, Pennsylvania and Wisconsin.

You’ll notice that I’ve referenced past presidential election results to determine how competitive the races for the House and Senate are. That’s important because straight-ticket voting is much higher these days than it used to be.

Looking at the two previous presidential election years, just once did a state vote for one party for president and another for the Senate (Maine in 2020). For reference, six states did so in 2012.

The same patterns between presidential and down-ballot voting holds true in the House as well. Only 4% of House districts voted one way for president and a different way for the House in 2020.

This is critical when thinking about this year’s House elections. A Newsday/Siena College poll of New York’s 4th District released Tuesday found Democratic challenger Laura Gillen ahead of the Republican incumbent, Anthony D’Esposito, by 12 points. The same poll showed Kamala Harris up by double digits among district voters.

Now, we don’t have district polling for the other three New York seats I mentioned earlier, but forecasts indicate Democrats have a real chance to win them all. The 22nd District clearly leans Democratic, while the 17th and 19th are toss-up races.

This makes sense given that Siena’s New York state poll, also released Tuesday, found Democrats doing about 5 points better statewide in the House vote than they did in 2022. A swing like that applied to these four districts would see Democrats flip all of them.

Perhaps most importantly: Biden would have won all four seats in 2020 under the current lines.

One competitive House seat in the Empire State that Biden wouldn’t have won is the 1st District on Long Island. Under the new map approved earlier this year, district voters would have backed Trump by 2 points. Another Tuesday Newsday/Siena poll had Harris and Trump essentially even in the district. It made sense, therefore, that the same poll showed Republican Rep. Nick LaLota leading Democratic challenger John Avlon by a mere 3 points. That’s well within the margin of error, even though most forecasters have that race leaning or likely Republican.

The bottom line is that New York provides House Democrats with a lot of opportunities, and it’s not the only blue state that does.

California has another five Republican-held House seats that most handicappers say are toss-ups, at worst for Democrats. Biden would have carried four of them in 2020 under the current lines.

So it’s no wonder a Democratic takeover in the House is a real possibility: They have a lot of potential pickup opportunities in districts Biden won in states that he won.

Of course, Republicans could certainly hold the House, and something wacky could happen in the race for the Senate.

But at this hour, it’s not difficult to imagine congressional history being made next month – history that would both please and upset both sides of the aisle.

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