At a critical and last-chance moment for the contenders, Thursday’s Republican debate in Michigan offered voters the clearest view yet of their options going into November. There was John R. Kasich, the last results-focused governor standing. There was Senator Marco Rubio of Florida, who combines conservative economic orthodoxy with the foreign policy views of The Weekly Standard. There was Senator Ted Cruz of Texas, the slightly more populist, Wall Street-phobic version of a contemporary conservative. And then there was Donald J. Trump, who is — well, let’s just leave that to him.

Debates Are No Time to Attack Trump

Time and time again, anxious Republican leaders have urged their more conventional standard-bearers in the race to take on Mr. Trump. Thursday night’s debate showed why that almost never works. He talks over attack lines. He refuses to admit to flip-flops, even when pressed by a moderator or hemmed in by video footage. He blusters his way past fact-checkers and rivals alike.

By comparison, Mitt Romney’s lengthy takedown of Mr. Trump at a Utah university earlier in the day, a sober accounting of Mr. Trump’s heresies and weaknesses, felt more compelling than anything unleashed by the other candidates.

The problem for Mr. Trump’s opponents: There is really no good place or time to take him down. He waved off Mr. Romney’s attacks, too, dismissing him as just another loser.