Sixteen months ?into his second term, U.S. President Donald Trump may be as unpopular as he’s ever been among the American electorate — but his grip on his core base of MAGA voters remains unshaken.

That power was on full display over the last two weeks, as Trump ousted a string of fellow Republicans he considered apostates for not showing him enough personal fealty. The president’s revenge tour continued on Tuesday, when a hand-picked loyalist defeated U.S. Rep. Thomas Massie, a frequent critic, in a Kentucky nominating contest.

But Trump’s success in purging the party of dissenters could also hurt its chances of retaining control of Congress in November’s midterm elections, some Republican strategists said.