Since Sen. Bernie Sanders (I-Vt.) suffered a heart attack earlier this month, it has been an open question whether he would start winding down his campaign. His standing in the polls fell somewhat, and he has fallen behind Sen. Elizabeth Warren (D-Mass.), who is now neck-and-neck with former Vice President Joe Biden. The man is 78 years old, after all.

But Sanders made a significant comeback during and after Tuesday night's debate, with a sharp performance and the subsequent reporting of upcoming endorsements from rising progressive stars Reps. Alexandria Ocasio-Cortez (N.Y.), Rashida Tlaib (Mich.), and Ilhan Omar (Minn.). He is back in this thing.

Sanders spoke less than several other candidates during the debate, but what he did say was sharp and on point. His arguments were clear — especially in contrast to Biden, who as usual was rambling all over the place — and he got the best zinger of the night. When Biden boasted about his history of passing bills on a bipartisan basis, Sanders shot back:

"Joe, you talked about working with Republicans and getting things done. But you know what you also got done? And I say this as a good friend. You got the disastrous war in Iraq done. You got a bankruptcy bill, which is hurting middle-class families all over this country. You got trade agreements, like NAFTA and PNTR, with China done, which have cost us 4 million jobs."

Perhaps most importantly, Sanders did not appear at all like someone who had just suffered a heart attack — he was full of the same old energy, inequality statistics, and gesticulations as usual. Indeed, several commentators observed that it was his best performance of any debate so far.

The endorsements from three-quarters of "the Squad" (Massachusetts Rep. Ayanna Pressley, who is the most conservative of the group and also from Warren's home turf, unsurprisingly did not join the other three) also outlines one of the strongest arguments for the Sanders candidacy: his ability to turn out fickle young voters. In the 2016 primary, he absolutely crushed it among the youth vote, winning more young votes than Donald Trump and Hillary Clinton combined. This time, with so many other candidates, he is not cleaning up to quite the same degree, but most polls have found him far ahead among voters under 30.

I have no doubt that Ocasio-Cortez, Tlaib, and Omar would enthusiastically support Warren were she to win the nomination. But Sanders has been there for left-wing politics in a way that Warren has not — carrying the torch through the lonely 1980s and 1990s, when neoliberalism became the hegemonic dogma of both parties and Warren was still a registered Republican. The reason why Sanders leads among both young voters and rising young lefty leaders can be summed up in one word: credibility.

Now, Sanders will still have a difficult time actually winning. But there may yet be a path for him. The rest of the field clearly regards Warren as the frontrunner, despite the fact that Biden continues to lead in many polls. At the debate, she spoke the most, but only because she was being attacked by everyone except Sanders. If Sanders can convince voters his health is still good, and get his overall numbers up a few points, he could be in prime position to win in Iowa and New Hampshire, and from then have enough momentum and good press to continue to win overall.

Sanders also has a substantial money advantage — he raised more than any other candidate last quarter, has the most cash on hand, a lower burn rate than anyone but Warren, and is tied with her for the highest share of small-dollar donors. Indeed, he raised nearly $10 million more than Biden and has more than three times his cash on hand, probably in part because the Biden campaign spent nearly $1 million on private jets over that time — while Sanders famously runs his operations on the cheap.

It would surely be a risk to nominate an old man who recently suffered a heart attack (which is why Sanders' potential choice of running mate would be so important). But it would also be another kind of risk to nominate a younger person who is clearly up for sale — like South Bend, Indiana, Mayor Pete Buttigieg, who was talking about Medicare-for-all as the moderate compromise position before he raised a ton of money from the health-care industry and now is on the warpath against it. It is perfectly sensible to believe that Sanders represents the best bet for the next president of the United States. And he's still in that fight.

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