Most important, Mr. Trump has upended the strategic dynamics of recent Republican contests — the dynamics that have led people like Mr. Reed to predict his defeat.

“The key to being nominated has been to be the last man standing against a totally unacceptable candidate,” Mr. Reed said…

But Mr. Reed has an increasing appreciation for Mr. Trump’s political ability. For all of his rhetorical fireworks, he has driven home his simple vow to “make America great again.”

Mr. Trump “is the most on-message candidate of this cycle, by a factor of 10,” Mr. Reed said.