A New York City septuagenarian with nothing more than a handful of crazy ideas and a band of hardcore followers, hoping to become president of the United States? A wild-haired populist who’s openly running against the establishment of the same political party whose nomination he’s trying to win?

A guy like that can’t possibly wi … oh, wait.

I was at Bernie Sanders’ rally in Concord, N.H., on Sunday and, having covered the Trump campaign in 2016, it was Donald Trump deja vu all over again. The fevered zeal of the crowd, the unmoderated rhetoric of the candidate and — oddly — the dismissive attitude of the press.

Democrats desperate to dismiss Sanders as a serious contender do so at their own risk. They can insist he’s just leading a movement, firing up the fringe, etc. But Sanders doesn’t see it that way. He’s not running to make a point. He’s running to make it to Pennsylvania Avenue. And so far, it’s working.

Bernie Sanders is packing venues and powering up polls across the country. Sarah and Jacob, a local Concord couple, braved a snowstorm to see Bernie and told me, “We’re not really political people. This is the first rally we’ve ever been to.”

George W. Bush’s campaign “strategerist” Karl Rove is no Sanders fan, but he observes that since the first of the year, Sanders’ poll numbers have risen steadily, from around 16 percent of Democratic primary voters to 27 percent or so today. Meanwhile, Joe Biden’s numbers have been flat and Liz Warren — Sanders’ New Hampshire nemesis — has plunged.

But read the smart-set punditry from the D.C. crowd, and you’ll hear a lot of the same people making the same “yeah, but he can’t win” arguments they made about Donald Trump four years ago.

The Washington Post’s “Big Crowds But Some Doubt in Early States” was a typical headline. “He is not going to be the nominee of the Democratic Party,” said Clintonista and newly elected Florida congresswoman Donna Shalala.

Former DNC adviser Jamal Simmons calls Sanders “the MySpace or the Friendster of the Democratic left.”

“The campaign has moved beyond him,” Eileen McNamara of WBUR’s Cognoscenti wrote. “Bernie Sanders can be a leader helping to guide a new generation of political activists, or he can be a crusty septuagenarian refusing to surrender the stage. He can’t be both.”

Tell that to Abigail and Geri, two Nashua high schoolers who showed up to see a guy who could literally be their great-grandfather give a political speech. They’re not even old enough to vote, but they’re cheering Sanders on.

“He’s good at connecting with young people, he understands what they want,” said Geri, who also happens to be African-American. “I don’t see his age as a problem.”

“I do like some of the other Democratic candidates, but it’s just like, emotionally, they just haven’t appealed the same way, and they don’t have the same dedication that he has,” Abigail told me.

Oh, and they both made the point they’ll be old enough to vote by Election Day.

And yet establishment Democrats and their stenographers in the mainstream media continue to dismiss Sanders’ chances. My question is — who’s going to stop him?

Even as it continues to grow, the Democratic field of candidates looks smaller and smaller. Elizabeth Warren is on her last legs. Joe Biden is the Democrats’ Jeb Bush — the day he announces will be the best day of his campaign. Kamala Harris’s problematic past is beginning to catch up with her.

But nobody’s catching up with Bernie. There’s a moment in the movie “Rocky” when, early in the fight, Apollo Creed’s manager tries to get the champ to see the danger.

“He doesn’t know it’s just a damn show,” he says of Rocky Balboa. “He thinks it’s a damn fight.”

Democrats, welcome to “Rocky II.”

And remember who won that one?

Michael Graham is a regular contributor to the Boston Herald. Follow him @IAmMGraham on Twitter.