What a difference a year makes. When he launched his second presidential campaign, in February 2019, the independent senator from Vermont was mocked and written off by much of the pundit class. The Washington Post’s Henry Olsen called him a “one-hit wonder,” adding: “After a few concerts that attract ever more ‘selective’ audiences, he will likely drop out and retire, his influence consigned to history.” (On Monday night, a whopping 7,500 people turned out for a Sanders rally headlined by Rep. Alexandria Ocasio-Cortez, as well as rock band The Strokes, in Durham, New Hampshire.)

And yesterday, in New Hampshire, Sanders won with a narrow victory over former South Bend, Indiana, Mayor Pete Buttigieg. Biden came in fifth.

On Monday, he took the lead in a national Quinnipiac University poll for the first time in the 2020 Democratic race.

Last week, in the Iowa caucuses, Sanders won the popular vote by a clear margin in both the first and second rounds.

Bernie Sanders is now the undisputed frontrunner in the race for the Democratic presidential nomination.

On Twitter, Olsen’s fellow Post columnist Jennifer Rubin described Sanders as “yesterday’s news” and suggested he would face “stiff competition for youth vote” from Beto O’Rourke. (O’Rourke quit the race in November, while Sanders won almost half of 17- to 29-year-olds in Iowa and more young voters in New Hampshire than “all of the other candidates combined.”)

Yet another Post columnist, David Von Drehle, wrote how Sanders would find “that his moment is gone, his agenda absorbed by more plausible candidates, his future behind him.”

Then there was MSNBC host Chris Matthews, who claimed Sen. Elizabeth Warren would “blow out Bernie pretty early on. Bernie will lose his votes to her.” (Warren, for the record, came third in Iowa and fourth in New Hampshire.)

MSNBC political contributor Jason Johnson went even further: “I see Bernie Sanders launching his campaign and by August, realizing he won’t be in the top five in Iowa, and dropping out.”

Do they never learn? For the second presidential cycle in a row, the political pundits have had to eat crow. During the 2016 race, former Obama strategist David Axelrod dismissed Sanders as the candidate with whom Democratic voters would only “flirt” or have a “fling” with. The Vermont senator went on to win 13 million votes and 23 states.

Four years later, Sanders has come from behind to dominate the first two contests of the 2020 Democratic race. In Iowa, he declared victory while calling for a partial recanvass of the chaotic and messy results. Remember: Over the past four decades, no candidate has won in both Iowa and New Hampshire and then failed to win the nomination.

Sanders beat Buttigieg by only a narrow margin in New Hampshire — especially compared to his 22-point victory over Hillary Clinton in the Granite State in 2016. Yet a win is a win, especially in the crowded 2020 field, and the only democratic socialist in this race now has what the New York Times has rightly called “that most prized and nebulous of assets: momentum.” Up next are the Nevada caucuses on February 22, where only a single percentage point separates Biden from Sanders. In South Carolina, which goes to the polls on February 29 and where Biden once led by a whopping 31 points, Sanders has narrowed the former vice president’s lead to 8 points in the latest Zogby Analytics poll.

Biden, though, is in freefall: an embarrassing fourth in Iowa, a humiliating fifth in New Hampshire. Back in December, I argued on CNN that mainstream media organizations were ignoring the possibility that Sanders could win three of the first four states. In fact, he could now end up winning all four of them.

No wonder Democratic Party elites are panicking. We hear the same tired arguments about Sanders lacking “electability.” These arguments conveniently ignore the fact that Sanders beats Trump in head-to-head polling; that the Vermont senator is the most popular member of the Senate; and that this self-proclaimed socialist has both the highest “net favorability rating” among Democratic voters as well as the most enthusiastic base.

Plus, the only way to test “electability” is through actual elections, and so far Sanders is two for two.

Iowa and New Hampshire, though, weren’t only victories for the senator from Vermont; they were also victories for Sanders’s signature issue, Medicare for All. Asked last week in an entrance poll how they felt about “replacing all private health insurance with a single government plan for everyone,” 57 percent of Iowa caucus-goers said they backed it, while only 38 percent were opposed.

In New Hampshire, on Tuesday, again almost six in 10 voters said they supported a Medicare for All system over the current private insurance system, according to an early exit poll.

Yet again, the pundits and prognosticators were wrong. “Iowa Democrats worry ‘Medicare for All’ hurts key industry,” read the headline in the Associated Press in December. “In Iowa, Single Payer ‘Medicare For All’ Loses Ground,” declared Forbes in August. “Medicare For All Isn’t That Popular — Even Among Democrats,” proclaimed FiveThirtyEight’s Nate Silver a month earlier.

“We’ve heard a lot about how Bernie Sanders is so ‘wildly out-of-touch’ with the Democratic electorate,” observed CNN contributor Kirsten Powers on Tuesday night. “Well, that’s not actually true.”

The message from Iowa and New Hampshire is clear. It was a big, big mistake to write off both Bernie Sanders and his No. 1 policy proposal. So going forward, will his critics make that same mistake again?