There are signs former President Donald Trump’s determination to maintain an active role in GOP politics may be complicating his party’s bid to regain the Senate in next year’s midterm elections.

One persistent maxim of American politics is that the party that wins the White House loses congressional seats at the next midterm election. But recent history shows that far more consistently true for the House, which fills all 435 seats every two years, than for the Senate, where only one-third of 100 are contested.

In fact, in the last six elections occurring two years after election of a new president, the party in power twice gained Senate seats and twice lost only one. But it lost House seats in five of the six, mostly by double digits.

Since senators serve six-year terms, the group facing the voters in any midterm election consists of those elected in a presidential election six years earlier. Those up in 2022 were elected in 2016, an unexpectedly good Republican year, and 2010, an excellent one.

As a result, 20 of the 34 Senate seats on the 2022 ballot are now held by Republicans and 14 by Democrats. At present, analysts see only three Democrats facing potentially serious challenges: Sens. Catherine Cortez Masto of Nevada, Maggie Hassan of New Hampshire and Raphael Warnock of Georgia.

Of the three, Warnock probably faces the most difficult reelection since Georgia remains closely divided politically. A recent New Hampshire poll showed Hassan trailing Gov. Chris Sununu, but it is unclear if the popular GOP governor will run.

Still, the biggest prizes next year may be the open GOP seats. While all 14 Democratic incumbents seem likely to run again, five of the 20 Republicans have already announced they won’t: Sens. Pat Toomey of Pennsylvania, Richard Shelby of Alabama, Roy Blunt of Missouri, Richard Burr of North Carolina, Bob Portman of Ohio.

Three others, Sens. Chuck Grassley of Iowa, John Thune of South Dakota and Ron Johnson of Wisconsin, may join them.

Alabama, Iowa, Missouri and South Dakota have been pretty solidly Republican in recent years. But the Democrats would certainly have a fair chance to win non-incumbent Senate races in North Carolina, Ohio, Pennsylvania and Wisconsin, though they may also face damaging primary battles.

Their prospects might increase if the GOP rejects the establishment Republicans who have traditionally done well there and nominates outspoken Trump supporters with potentially less appeal to more moderate general election constituencies.

The entire situation echoes 2010 and 2012, when more conservative GOP candidates lost general elections after beating establishment Republicans in Senate primaries. That helped the Democrats maintain their Senate majority for four years after they lost the House in 2010.

Donald Trump has already made clear he will oppose his foes and help his supporters in 2022. He vowed to campaign against Sen. Lisa Murkowski, who voted for conviction in Trump’s January impeachment trial.

In Ohio, four candidates, including former state Treasurer Josh Mandel and former GOP chair Jane Timken, are jockeying for Trump’s support. Though the former president twice carried the state, the most successful Ohio Republicans have been more moderate candidates such as Portman, Gov. Mike DeWine and former Gov. John Kasich.

In Pennsylvania, which Trump won in 2016 but lost in 2020, moderate former Rep. Ryan Costello’s prospective candidacy has drawn strong opposition from the former president’s adherents. But when the GOP nominated Trump supporter Lou Barletta in 2018, he lost to Democratic Sen. Bob Casey by 13 points.

In recent weeks, Senate Republican Leader Mitch McConnell, who precipitated a major GOP row when he criticized Trump for challenging the 2020 results and encouraging the Jan. 6 Capitol insurrection, has wisely indicated a pragmatic approach to 2022.

“What I’m looking for is somebody who can win in November,” he told CNN. “It’s not a ‘who do you think is going to be the nominee in ‘24’ thing. It’s can you win in November?”

Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News.