If his approval numbers inch down and support for impeachment and removal grows, the outlook for these Republican senators — and others — might become even more bleak. And they may start considering options to buy a reprieve that would be helpful to their re-election chances but harmful to the president: If they are so inclined, they might give more private thought of voting to remove Mr. Trump from office. Or they might be more open to a symbolic vote to convict and remove, knowing not enough other Republican senators would follow. Either one of those scenarios hurts Mr. Trump’s political fortunes by lending legitimacy to the impeachment process.

The lesson to be taken by the Republican Party from the Bevin debacle is that senators and others need to work on their own images and reputations to seal the deal with voters — and apart from Mr. Trump and his popularity with his base, which might not be transferable. He couldn’t elevate Mr. Bevin, and his own data as well as public polling indicated that he should have. He’s not going to be the savior of Senators McConnell, Ernst, Gardner or Collins, either — and all of them should be planning accordingly.