For Vermonters who share a 40-year history with Bernie Sanders last night’s debate was important in that he looked healthy, he was warm in thanking those who thought of him during his convalescence, and he was able to put to work his wit and humor. For anyone expecting his support to dissipate like the morning’s fog, there was also the announcement that Rep. Alexandria Ocasio-Cortez, D-N.Y., the darling of the far left, will be endorsing Mr. Sanders this weekend.

Clearly, the fire continues to Bern.

In the largest sense of things, that’s what is important. No one wishes Vermont’s junior senator to be anything other than healthy. Even the one-percenters. Mostly.

His health was the subject of inquiry, as was expected. It could not be otherwise. But he handled the questions thoughtfully and with uncharacteristic warmth, using the opportunity to offer heartfelt thanks to those who sent their thoughts and prayers. It was a side of the senator, the public doesn’t see.

That’s the story important to Vermonters, it was only a small part of what was happening on stage. Mr. Sanders was not the target. Nor was Joe Biden. The target was Elizabeth Warren, the senator from Massachusetts, the senator who has overshadowed Mr. Sanders on his own turf. It’s Ms. Warren who has pulled even with Mr. Biden in the polls, and in some states, is convincingly ahead.

Mr. Biden did well enough in the debate, but like the smell of blood in the waters, the moderates have begun to circle, smelling the opportunity that comes when vulnerability is sensed. If President Trump succeeds in crippling Mr., Biden’s candidacy, a distinct possibility, there will be an opening for those Democrats who believe Ms. Warren is too liberal, that her boldness will be a liability in a general election.

Their chance is now.

That opportunity, and what defines it, will be the debate going forward. Eight more debates are scheduled and the next four, to be held before the Iowa caucus, will draw out these vulnerabilities. It will be over the next 100 days — the snap of a political finger — that the numbers will begin to solidify and the various camps will take stock of their positions and how they may use them to affect the outcome. [Is Senator Cory Booker positioning himself for someone’s Vice President?]

There is also the understanding in politics that a minute is an eternity, anything can happen, and has. Mr. Sanders is proof positive. Being sidelined with a heart attack was not in his playbook. But if Mr. Biden is slipping and if the reason can be attributed to him being the target of both the president and his fellow challengers, then the open question is whether Ms. Warren can handle the same level of questioning.

If every day were to be a repeat of last night’s performance, her worries would be limited. But they won’t be. There is every indication Mr. Trump would welcome her as his ideal challenger. He won in 2016, in no small part, because his supporters opposed the educated elite that Hillary Clinton represented. And who better represents the educated elite than Ms. Warren, a professor of law at Harvard University?

What we will learn in short order is what sort of hold the far left has on the Democratic Party and the 12 remaining challengers. Will bold ideas fall to the moderates’ push to have Mr. Sanders and Ms. Warren come clean with the voters in terms of what they are proposing costs and who will pay what and when? And does that inquiry help revive Mr. Biden’s support?

We’ll see. The only thing that’s certain is that as the other candidates twist and turn to position themselves most favorably, Mr. Sanders won’t. And, as we saw last night, he’s still a player.

by Emerson Lynn