John Kasich

The GOP nominee

The GOP nominee

Well, America — or at least those 11 million or so voters who cast a plurality of ballots in the Republican presidential primaries and caucuses — you asked for him, and you've got him: Donald Trump is now the party's presumptive nominee. The departures of Sen. Ted Cruz and Gov. John Kasich from the political battlefield after their lopsided Indiana losses on Tuesday means any reasonable hope of a contested Republican National Convention has officially left the building.

What seemed unimaginable last June, then hard to believe, later possible and eventually probable is now reality and not merely a made-for-television spectacle. Let this sink in for a bit: Donald Trump,...