Trump’s Primary Losses Puncture His Invincibility

Donald J. Trump had cast this year’s primaries as a moment to measure his power, endorsing candidates by the dozen as he sought to maintain an imprint on his party unlike any other past president.

But after the first phase of the primary season concluded on Tuesday, a month in which a quarter of America’s states cast their ballots, the verdict has been clear: Mr. Trump’s aura of untouchability in Republican politics has been punctured.

In…