The impeachment effort against Defense Secretary Pete Hegseth posed a dilemma for Republican leaders ahead of the midterms. In the lame duck, it could be Democrats in the bind.

Hegseth is leading an unpopular war in Iran, and GOP leaders were eager to avoid an impeachment vote this month, which would have put some vulnerable Republicans in a tough spot heading into November’s elections. Speaker Mike Johnson (R-La.) defused the issue by punting that vote until after the elections.

But the tides are likely to turn after the election, when Republicans will be freed to weigh in on Hegseth’s fate without fear of a voter backlash, while Democrats will face a tou...