In Des Moines, Mr. Trump, who took a swipe last year at Senator John McCain of Arizona for being “captured” in Vietnam, and long before that complained that “homeless veterans” were ruining his property values, made the night air sparkle with his praise. And soon, like a true ringmaster, he gave the people what they wanted — three real, live veterans who came onstage to speak to the crowd.

As someone who spent 20 years in the active-duty Army, I should be used to strangers bending and twisting my service to suit their needs. But I’m not. I’ve been out of uniform for nearly a decade, and I still break out in a rash when I see service members used, misused and abused for commercial or political gain.

For candidates, veterans are the most useful props imaginable. They are real-life stand-ins for any number of campaign trail virtues: patriotism, national defense, antielitism, take your pick. And they are a great way to inoculate oneself from criticism for not having served — which is the case for every major candidate in the 2016 race, not just Mr. Trump. (The former Virginia governor Jim Gilmore, a long shot, is the exception.) Still, for Mr. Trump, who avoided military service in Vietnam, this was a particularly blatant and distasteful ploy for credibility.

But the public gets something out of the bargain, too. For many, to be in a room with a veteran is to touch the battlefield. In his novel, “Billy Lynn’s Long Halftime Walk,” Ben Fountain describes the quasi-religious ecstasy that can come about when civilians meet so-called war heroes: “They tremble. They breathe in fitful, stinky huffs. Their eyes skitz and quiver with the force of the moment, because here, finally, up close and personal, is the war made flesh.” Mr. Trump hoped his supporters would skitz and quiver their way right into his campaign coffers.

At least there was a payoff. The $6 million Mr. Trump promised to donate to veterans organizations is, as Forbes recently pointed out, $5.94 million more than his charitable foundation has given veterans in recent years. Though some veterans organizations have said they’ll take the money raised at the event, the Iraq and Afghanistan Veterans of America, a group that represents about 150,000 veterans, has said no thanks. The I.A.V.A.’s founder, Paul Rieckhoff, tweeted: “We need strong policies from candidates, not to be used for political stunts.” Mr. Rieckhoff was right to refuse the candidate’s cash, and put some distance between veterans and Mr. Trump.