An inside view of the US Senate.

Stuart Rothenberg, Tribune News Service

Though it’s far from a sure thing, it now looks very possible that both the House and the Senate will flip in 2024, putting the “out” party back in control in each chamber in 2025.

How unusual would that be? Well, according to the US Senate Historical Office, it has never happened. Ever.

Obviously, the 2024 elections depend on the presidential tickets, candidate recruitment and retirements in the House and Senate, the state of the economy and dozens of other factors. But given how weird American elections have become, maybe the fact that two flips in different directions have never happened is reason enough to bet it will occur next year.

It’s not all that unusual when one party gains seats in the House and the other party gains seats in the Senate. It has happened more than half a dozen times since 1970, including the last three elections.

In 2022, Democrats added a Senate seat but lost seats in the House. Two years earlier, Democrats gained three Senate seats while Republicans gained a dozen House seats.

And two years before that, during President Donald Trump’s 2018 midterm elections, the GOP gained a couple of Senate seats while getting clobbered in House races.

Republicans added Senate seats in 2018 because of the nature of the seats up for election. The GOP was defending just nine Senate seats that year, while Democrats were defending 26. The Democratic seats at risk included conservative states such as Indiana, Missouri, North Dakota, Ohio and West Virginia — all of which had gone comfortably for Trump in the 2016 presidential election.

The House, on the other hand, flipped to the Democrats because Trump, the incumbent president, was widely unpopular, particularly in upscale suburbs that found his personal behavior and rhetoric offensive. And he was hurt by the midterm dynamic, which tends to turn out voters who are disappointed or angry about the president’s performance in office.

Why is it possible that both houses of Congress could flip control in 2024, with the Senate going from Democratic to Republican and the House flipping the other way, from Republican to Democratic?

On the Senate side, a huge Democratic class will come up for election in 2024. The class includes Joe Manchin III of West Virginia, Jon Tester of Montana and Sherrod Brown of Ohio, all of whom represent states carried comfortably by Trump in both 2016 and 2020.

Yes, all three Democrats won reelection in 2018, so they have proven their electoral mettle. But that was during a midterm cycle with an unpopular Republican in the White House. Joe Biden lost all three states in 2020, and, given the states’ partisan bent, it’s likely that the Democratic nominee for president next year will lose all three states again in 2024.

Republicans also have other Senate opportunities in very competitive states currently held by Democrats, including Wisconsin (Sen. Tammy Baldwin), Nevada (Sen. Jacky Rosen), Pennsylvania (Sen. Bob Casey) and Michigan (Sen. Debbie Stabenow, who is retiring, creating an open seat). Of course, having opportunities is not the same thing as winning seats, as the GOP found out last year. But at this very early point in the 2023-24 cycle, Republicans seem well positioned to net at least two Senate seats, which would give them control of the Senate in 2025.

But if 2024 looks like a good opportunity for the GOP to flip the Senate, it also looks like a possible Democratic opportunity to win back the House after just two years of Republican control.

Democrats need to net just five House districts to win back control of the chamber, and, unlike in the Senate, Republicans will be defending more Biden districts than Democrats are defending Trump districts. Eighteen Republicans currently sit in districts carried by Biden, while only five Democrats sit in districts carried by Trump in 2020.