Mr. Trump’s preferred candidates in key states are struggling or close in the polls despite the favorable GOP trends. Mehmet Oz is trailing left-wing Democrat John Fetterman in Pennsylvania. Herschel Walker is a rookie candidate showing his inexperience in Georgia. and Rep. Ted Budd is barely ahead in North Carolina. As in 2010, Democrats could prevail against a slate of weak GOP candidates.

It’s possible that voter unhappiness with the Democrats may be so strong that it swamps any concern with Mr. Trump, who after all will not be on the ballot. Glenn Youngkin was able to win the statehouse in Virginia in part because Mr. Trump largely stayed out of the race.

But that was a rare exception, and Mr. Trump typically can’t help himself. He wants to be the center of attention all the time, and the media are all too happy to oblige. All the more now when his preoccupation is overcoming the stigma of his defeat in 2020 by sticking to his stolen-election line. If Republicans fall short of the gains they expect in Congress, he’ll blame them. If they do well, he’ll claim credit.