In the wake of the FBI’s search of his Mar-a-Lago estate, Donald Trump has boosted his fundraising, fired up his conservative supporters and helped vanquish Liz Cheney, arguably his biggest Republican foe.

But the former president’s return to the fore of America’s political stage, with a barrage of seething rhetoric and under a cloud of serious legal trouble, risks blunting the Republican party’s advantage heading into the midterm elections by alienating swing voters at a time when it was already showing signs of ebbing.

“He’s inflaming our politics continually, and it’s inflaming Republicans but also inflaming Democrats,” said Michael McDonald, a political-science professor at the University of Florida. “If he just stepped back?.?.?.?Republicans would have been in a much better position than they are right now. But he’s still exerting himself.”