The Democratic race for president is shaping up as most of the candidates expected at the outset, with the campaign appealing to the most fervent progressive wing of the party showing formidable strength.

It’s just that Bernie Sanders is the one running that campaign.

At the beginning of the race, everyone wanted to hug Bernie in the hopes of replacing him. They’d be younger, more diverse, fresher, more acceptable to the Democratic mainstream, or more electable than the old, white, male socialist standard-bearer.

Who could resist getting everything that Sanders stands for in a more politically palatable vehicle? The answer seems to be Democratic voters.

The would-be Bernie epigones, who became uncertain over time whether that’s what they really wanted to be, have dropped out of the campaign or, in the case of Elizabeth Warren, lost altitude, while Bernie has a serious shot at building a head of steam toward the nomination.

The Bernie model is working for Bernie where it failed everyone else.

The foremost reason is authenticity. No one believed that Cory Booker, Kirsten Gillibrand or Kamala Harris was a progressive warrior. Yet all of them endorsed his version of “Medicare for All,” the Vermont’s socialist signature proposal that would represent the most intrusive expansion of government in American history.

The plan would impose a more restrictive and generous government-run health care system on the U.S. than exists in European social democracies. It’s not something you endorse lightly, but Booker et al. did. They all wobbled or flip-flopped, demonstrating, if there were any doubt, their insincerity on a key issue with deep philosophical implications.

Warren has suffered from the same disease. She has lasted much longer than the others. She also went much further down the Bernie path than the others, before an agonizing climbdown on Medicare for All.

Warren’s struggles played against a backdrop of her other authenticity problems, whereas Sanders has no such issues — in fact, the opposite.

No one can match his socialist cred, built up over decades. Only Bernie honeymooned in the Soviet Union. Only Bernie has videos out there praising Castro. Only Bernie has never formally joined the Democratic Party. Only Bernie took on the party establishment single-handedly in 2016, and almost won.

Sanders says things that are fantastical and untrue all the time, but out of sincere belief in his program. He’s shifted on issues like guns and immigration over the years, but still gives the impression more than any other major politician of simply being incapable of going out and mouthing poll-tested bromides that he doesn’t believe.

His small-donor fundraising base gives him an independence from traditional Democratic donors and their world that no other major candidate has.

If Sanders is going to win the Democratic nomination, it is going to be, like Trump on the Republican side in 2016, as a total rejection of every aspect of his party’s establishment — its preferred policy mix, its traditional strategic thinking, and its personnel.

This politics of disruption necessarily entails avoiding half-measures, compromises or inhibitions. With Trump, this meant staking out stark positions on trade and immigration, and never toning down his personal outrageousness; he was always doubling down. With Bernie, it means proposing a massive program of taxes, spending and regulation without apology or hesitation, and never bowing to conventional Democratic thinking; he, too, is always doubling down, although on substance and political strategy rather than tweets.

The clear message, from Trump in 2016 and Sanders now, is that the old rules don’t apply, not even a little bit.

You can’t adopt this posture occasionally, or while trying to keep a foot in both camps, or with an eye to a pivot in the general election. You have to be all in. If you want to be Bernie Sanders, you have to be Bernie Sanders.

Rich Lowry is editor of National Review.