As a vice presidential pick, JD Vance has been a big mistake, as even some of Donald Trump’s Mar-a-Lago mafia and media friends concede.

A younger version of Trump, Vance brings no new voters to the Republicans’ side; their ticket is MAGA squared. He’s likely lost more than a few votes, by maligning millions of “childless cat ladies” — not least pop icons Taylor Swift and Jennifer Aniston. He spends much of his time on the defensive for past comments, even as he creates new controversies on his rounds of right-wing podcasts, talk-radio shows and conservative conferences. Instead of cleaning up his messes, he doubles down, allergic (like Trump) to apology. And Trump, confronted more than once about something Vance has said, dismissively notes he hasn’t spoken with his would-be veep. Ouch.

Yet as rotten a second banana as Vance is, he’s a downright disaster at his day job: U.S. senator for Ohio.

Most officeholders pride themselves on providing good constituent service, especially in troubled times. Vance, bizarrely, is suddenly the uncontested master of constituent disservice, to the point of putting lives at risk.

The problems he’s made lately for tens of thousands of his constituents in Springfield, Ohio — all to demagogue the immigration issue — amount to political malpractice, the likes of which we’ve never seen before as Trump is so fond of saying about almost anything. Only this time it’s true.

For weeks, Vance has singled out Springfield as the epitome of a (white) American community overrun by people of color from another country — in this case, Haitians who’ve fled their nation’s epic poverty and violence to settle legally in Ohio, welcomed by employers desperate for hard workers. Vance, who once wrote so movingly about “hillbilly” families like his own coming to Ohio from Kentucky, seeking opportunity but enduring hostility, is so intent on advancing politically that he’s now the hostile one.

And once Trump picked up Vance’s lies about Haitian immigrants stealing and eating Springfieldians’ cats, dogs, ducks and geese — broadcasting the conspiracy talk to 67 million people who watched him debate Kamala Harris on Tuesday last week — all hell broke loose for Vance’s constituents.

Despite local officials’ assurances from the start that the reports were social-media-spawned claptrap, more than 30 bomb threats closed city hall, two elementary schools, two hospitals and two universities for a time. The threats, which have continued this week, turned out to be hoaxes. But the fear and disruption in Springfield were real. By Tuesday, Ohio Gov. Mike DeWine had dispatched state troopers to Springfield schools to encourage frightened parents to send their children to class, even as he warned of hate groups descending on Springfield. “It makes me sad that we have to get to this point,” one mom told the local paper.

Indeed. But her senator wasn’t sad, just mad — that he’s getting bad press. Consider this snippy, selfish tweet from Vance on Tuesday: “I’m still waiting on a correction and apology from the left wing journalists. They lied about these bomb threats to silence us. Why? Because they don’t want to talk about Kamala Harris’s border policies making housing unaffordable for American citizens.”

Apology? Reporters didn’t lie; there were bomb threats. Those trying to silence Vance’s fear-mongering aren’t journalists but Springfield’s police chief, school superintendent, Republican mayor and governor. Springfield Mayor Rob Rue has repeatedly implored Vance and Trump to stop: “All these federal politicians that have negatively spun our city, they need to know they’re hurting our city, and it was their words that did it.”

And “left wing journalists” aren’t the only ones checking Vance’s falsehoods. Conservative commentator Kevin D. Williamson this week had the best take in a Dispatch article subtitled “A pretty long story about a thing that didn’t happen”: “You can send little J.D. to Yale to make him polished, you can send him to Silicon Valley to make him rich, and you can send him to the Senate to make him powerful, but you cannot stop him from being what it is he apparently wants to be: Cleetus the Gap-Toothed Twitter Troll.”

Speaking of apologies, Vance has yet to offer one to Nathan Clark, the father of an 11-year-old boy killed last year in a bus accident. Clark publicly asked Vance to apologize for exploiting his son’s death as murder by a Haitian immigrant.

DeWine, meanwhile, has been all over television fact-checking Vance’s whoppers. Far from pet eaters, the Haitian residents are valuable employees at Springfield businesses who’ve lifted the local economy, the governor said on Sunday on ABC’s “This Week.” He acknowledged, “When you go from a population of 58,000 and add 15,000 people onto that, you’re going to have some challenges” — housing, healthcare, language and cultural differences. “And we’re addressing those.”

Not Ohio’s junior senator. “If I have to create stories so that the American media actually pays attention to the suffering of the American people, then that’s what I’m going to do,” he defiantly told CNN on Sunday.

The cardinal rule for vice presidential picks is do no harm. Vance is doing plenty. Which is why he’s a terrible nominee, and an even worse senator.

@jackiekcalmes