During an interview in Washington on Thursday, The Post’s Robert Costa tried his best to get Democratic presidential candidate and South Bend, Ind., Mayor Pete Buttigieg to say something negative about fellow candidate Joe Biden. Part of the old guard? Defended credit card companies? Responsible for mass incarceration as a result of the 1994 crime bill?

But each time, Buttigieg calmly sidestepped the invitation to go after the former vice president, while using the opportunity to lay out policy differences (“I have a difference of opinion with anybody who favors credit card companies over consumers”), and demonstrating his wonkish knowledge. “And when you look at the circumstances that lead to violence and other harms, you look at the kind of adverse childhood experiences that can set somebody back in life: exposure to violence is one, exposure to drug use is one, incarceration of a parent is one,” he said in discussing the 1994 crime bill. “So, the mass incarceration that may have felt in a knee-jerk way as a way to be tough on crime in the ’90s is now one generation later being visited upon communities today through the absence of parents.”

The politicians who have spent decades in politics rarely show the sort of poise Buttigieg naturally exhibits. That’s not nothing.

Buttigieg’s bluntness, succinctness and even-keeled delivery help him score TV-memorable points. During the same interview, he went after President Trump’s “bone spurs” excuse to get out of fighting in the Vietnam War: “If you’re a conscientious objector, I’d admire that. But this is somebody who, I think it’s fairly obvious to most of us, took advantage of the fact that he was the child of a multimillionaire to pretend to be disabled so that somebody could go to war in his place.”

Is the president a racist? “If you do racist things and say racist things, the question of whether that makes you a racist is almost academic,” Buttigieg said. “The problem with the president is that he does and says racist things and gives cover to other racists.”

Buttigieg also has begun to use his military service to his advantage. As someone who served in Afghanistan, his response to Trump’s promise to pardon war criminals was a particularly effective. He explained, “If you are convicted by a jury of your military peers of having committed a war crime, the idea that the president is going to overrule that is an affront to the basic idea of good order and discipline, and to the idea of law, the very thing we believe we’re putting our lives on the line to defend.”

In addition, Buttigieg seems comfortable (unlike some of his opponents) in discussing foreign policy. “Tariffs are taxes on Americans — and we talk as if that’s not the case; we forget that Americans are paying them,” he said, sounding like Republicans used to sound before they sold their souls to the devil. In place of tariffs, Buttigieg said we need to deal with China by, among other things, investing in our competitiveness, having a “more orderly disentanglement” of 5G technology and creating “a global framework” where China operates on our terms. (That’s not much detail, but as we know from polling, most voters don’t focus on the topic; they know China is misbehaving, they want someone to solve it in tandem with allies and they like to keep focusing on domestic initiatives that make us stronger.)

When asked what he’d do if Russia again interfered in our elections, Buttigieg said that Russian President Vladimir Putin should expect a “very serious response.” He then explained that “economic, diplomatic and cyber” responses, “both overt and covert,” would be needed.

Without getting into the weeds — which he will not likely be forced to do in a Democratic primary geared toward domestic issues — Buttigieg comes across as calm, informed and disinclined to saber-rattling (which he specifically criticized with regard to Iran).

In sum, Buttigieg stands out because he is remarkably disciplined, can effortlessly show expertise and projects authority on foreign affairs. Most of all, he displays the cool demeanor and wry humor that Democrats admired in President Barack Obama. After Trump’s irrational, loud, insult-driven rhetoric, it’s rather calming listening to Buttigieg.

Buttigieg has a long way to go in fleshing out policy proposals, and in broadening his appeal to minority voters, but …

The politicians who have spent decades in politics rarely show the sort of poise Buttigieg naturally exhibits. That’s not nothing.