He endorsed Mr. Romney with the broad-stroke simplicity of a parent describing a superhero to a scared child. “He’s not going to allow bad things to continue to happen to this country that we all love,” he said.

As he spoke, the Romneys stood off to Mr. Trump’s right with slight smiles and hands folded at their waists. Per custom, Mr. Romney stood like a ramrod and kept his smile firm, but lapsed into a slight toe-bounce at one point, signifying possible — well, who knows? (Sometimes a slight toe-bounce is just a slight toe-bounce.)

Mrs. Romney is the lesser poker player. Her cheeks grew increasingly red through Mr. Trump’s remarks, and she appeared on the verge of either laughter or terror during the whole show.

When it was Mr. Romney’s turn to speak, Mr. Trump assumed his place next to Mrs. Romney, and they stood together as an adoring couple joined in the service of Mr. Romney. While the Trump default face is one of pure satisfaction, the maven looked every bit the proud father when the candidate lauded “Donald Trump’s magnificent hotel.” As always, Mr. Romney reminded everyone that he had spent his life in the private sector — but added the caveat that he was “not quite as successful as this guy,” and Mr. Trump nodded the slow nod of a great man for whom respect had been paid.

Big ticket imprimaturs have proven consistently worthless in this campaign — evidenced Gov. Nikki R. Haley’s backing of Mr. Romney in South Carolina (he was pummeled by Mr. Gingrich) and Mr. Gingrich’s nod from Herman Cain before the Florida primary (Mr. Romney won handily). Easily lost in the media catnip of the announcement was the question of whether Mr. Trump’s support would compel a single person to vote for Mr. Romney.

The notion that it might was cast as absurd throughout the day by Mr. Romney’s rivals. “I can’t decide who to support,” wrote Jon Lovett, a former speechwriter in the Obama White House in a Twitter message. “I guess I’ll take my lead from one of America’s more garish and despicable figures.”

In his drive-by remarks, Mr. Romney stayed tethered to the electoral matter at hand, saying he was focused on securing the “endorsement of the people of Nevada.” He thanked Mr. Trump again, if nothing else for helping him to bury the unpleasantness of Wednesday — Mr. Romney’s “not caring about the very poor” remark — and the shower of glitter he received from protesters in Minnesota (or “confetti,” as Mr. Romney tried to spin it).

By remarks’ end, the big question remaining was whether the Mane Men would consummate their alliance with a hug. Nope, no hug. Instead, they locked in a long and showy handshake that — by the looks of Mr. Romney’s slight cringe and pulling-away posture — seemed like it might have hurt a little.