In a recent interview on “Meet the Press,” Ohio’s Republican governor, John Kasich, hinted that he may challenge President Trump in the 2020 GOP primaries.

This is all nice to gossip about, but is it practical? It depends on your goal. Primary challenges to sitting presidents rarely succeed in defeating them for renomination — in fact, it hasn’t been done since the 1850s. But such intraparty challenges often work in driving sitting presidents from office. That may be Kasich’s real objective.