Bob Kerrey served in the Senate with John McCain, is also a Vietnam veteran and has run for president, so he has been asked incessantly over recent days to appear on television and weigh in on Donald Trump’s vile besmirching of McCain’s military record.

He accepted only one of those invitations, from a friend. Otherwise he mostly stayed mum, lest he abet Trump’s ultimate goal, which is to turn his name into a news media mantra: Trump, Trump, Trump.

But on the phone on Tuesday, Kerrey’s frustration — no, let’s call it disgust — boiled over, and he, too, talked about Trump, Trump, Trump. I recount our conversation because I think Kerrey speaks for most Americans and because his comments capture what a conundrum many of us face.

If we discuss Trump, as I’ve done in several columns, we reward his bad and transcendently self-serving behavior, no matter how negative our assessments of him or how many larger truths we engage.

If we don’t discuss him, we ignore something real, in a fashion that’s irresponsible.

By something real, I mean the fact that Trump has measurable support, at least for now. In a nationwide ABC News/Washington Post poll of Republicans and Republican-leaning independents that was released Monday, he was in the lead for the party’s presidential nomination, the favorite of 24 percent of respondents. The next closest contenders were Scott Walker (13 percent) and Jeb Bush (12).

And yet.

“This is not a national primary,” Kerrey said, noting that Trump’s 24 percent has dubious predictive power for a consequential handful of individual contests in early states that aren’t exactly mirrors of America. “So who the hell cares what his numbers are nationally?”

“He’s not going to do that well in Iowa,” Kerrey continued. “There’s nothing about Trump that indicates that the evangelical community there is going to embrace him. And does anyone seriously think he has the kind of ground organization in New Hampshire to turn people out to vote?”

“He’s got no ground game,” Kerrey continued. “It’s all up in Donald’s head! Everything’s in Donald’s head. It’s the political version of ‘Being John Malkovich.’ ”

“The people running the networks know this,” he added, sighing. But they deliberately play it down as they seize almost every opportunity — including the McCain insult — to Trump anew and to Trump ad nauseam.

Kerrey groaned. “They’ve got a good sideshow going: ‘Are veterans offended?’ ‘Donald, are you going to apologize?’ For insulting McCain? He’s been insulted by better than Trump.”

Television has succumbed to the mantra more than other media, because it in particular thrives on theater, which Trump provides in excess. But those of us at newspapers and websites have definitely done our part, uncertain of the best approach.

The Huffington Post’s answer was to relegate Trump coverage to its entertainment section, explaining that he’s putting on a show, not running a serious campaign. So it was there that readers found a story about Trump’s latest attention-getting prank: During a televised rally on Tuesday, he ratcheted up his continuing feud with Senator Lindsey Graham by publicly divulging Graham’s cellphone number.

But for all Trump’s antics and nonsense, he placed second to Bush in a New Hampshire poll late last month. In a more recent Iowa poll, he trailed only Walker.

Kerrey conceded: “I don’t think you can really ignore it. But you have to evaluate, with some expertise, what his odds of being the Republican nominee are. And they’re practically zero.”

“Yeah, 5,000 people showed up at your event,” he said. “I could get 5,000 people to show up at the bearded lady. He is, in his way, a freak show.”

Kerrey thinks that Trump is principally interested in promoting his brand and padding his net worth, even if he has perhaps suffered a few short-term setbacks because of companies’ severing ties with him.

I think that Trump has an ego as ravenous as they come, with dimensions remarkable even for the political arena, and that his presidential bid is a splendiferous buffet for it. Watch it sup. See it swell. Look now: It’s a marvelous blimp.

But is his engorgement our debasement?

“It is not good for American politics,” Kerrey said.

I noted that some of his fellow Democrats were reveling in Trump, who was causing the Republican Party grief.

“I’m not putting my partisan hat on,” Kerrey said. “I’m putting my American hat on and saying: I want us to elect a great leader. And it’s going to be difficult as it is, because the money spent will be in the billions. It’s going to be hard enough to keep our balance and select a great leader even without this clown.”