Bernie Sanders performed brilliantly in Tuesday night’s debate. He was vigorous, sharp, and uncharacteristically relaxed, and even gracious. He was consistent and forthright in articulating his distinctive, “democratic socialist” vision, based on the mobilization of a mass movement (“political revolution”) centered on “the working class.” I have doubts about whether this vision can power a winning campaign in either the primary or the general election; the obstacles are great, and the risks of electoral failure also great. But it is beyond doubt that Sanders is a sharp-thinking man of vision and integrity, who cuts through the crap, and stands for egalitarian values, more clearly than any other candidate.

If his performance gave his campaign a much-needed boost in the wake of his recent heart attack, an even bigger boost will arrive this coming weekend when, it is being reported, Alexandria Ocasio-Cortez will join him at a rally in Queens and endorse him (it is also being reported that Rashida Tlaib and Ilhan Omar will endorse him too).

I have long sung the praises of AOC. She is a brilliant politician, a smart, dedicated, and charismatic young woman who has used her platform to articulate important values and policies and to work collaboratively with other Democrats on legislative issues. She has done an excellent job of straddling the fine line separating the roles of an elected official on the “inside” and an insurgent and political organizer on the “outside.” And she has done an equally fine job of owning her commitment to “democratic socialism” and at the same time avoiding ideological stridency and appealing to common sense.

It has been interesting to watch her throughout the current primary season. She has been very publicly close to both Sanders and Warren without endorsing either of them, she has also publicly worked with a wide range of other Democratic legislators, including presidential contender Kamala Harris (with whom she partnered on a housing bill and a climate justice bill), and she has gone so far as to develop a working relationship with Ted Cruz).

Her instincts have been good ones, and they seem to have been grounded in the kinds of arguments recently advanced by Nation editor D.D. Guttenplan in his “We Don’t Have to Choose Between Warren and Sanders Yet”: “‘Their truce during the 2020 campaigns is widening the left lane, and that’s good for everyone.” And yet, as Guttenplan acknowledged, the time for choosing would soon come, and people on the left will eventually have to choose. It now appears that AOC has chosen.

There are some risks in this (more below). But the choice is also understandable, justifiable, and wise, for these reasons: (1) AOC cut her political teeth on Sanders’s 2016 campaign, and his support and mentorship of her has played an important role in her political evolution, and political gratitude is a genuine virtue when it is principled; (2) Sanders is the presidential candidate whose policy positions and general commitment to “democratic socialism” align most closely with that of AOC; and, perhaps most importantly, (3) AOC is a movement politician, who understands her indebtedness and dynamic relationship to Democratic Socialists of America and to Justice Democrats, and by endorsing Sanders, she is also doing what most of her own “base” wants. It would be safer for her to remain neutral, at least between Sanders and Warren, for now. But she doesn’t play it safe, and she isn’t in DC to go along; she is there to make change. Her endorsement of Sanders, now, is bold, understandable, and even admirable, and it contributes to the further growth of left organizations with which AOC aligns, and I say this as someone who continues to lean toward Warren while watching how the contest unfolds.

At the same time, there are risks to AOC’s Sanders endorsement.

One is that while Sanders was sharp and vigorous on Tuesday night, there is a legitimate question about his health: whether he can continue a grueling campaign without suffering heart problems, and whether he can plausibly claim to be a strong candidate to occupy the Oval Office for four years, at his age and after having just suffered a heart attack. These are real questions; one simply needs to consider how the presidency aged two much younger and more healthy men, Barack Obama and George W. Bush. If Sanders can remain in the race, AOC’s endorsement will have proven beneficial. But if he is forced by circumstance to drop out, her “slighting” of Warren might prove somewhat problematic for her.

A second risk relates less to AOC than to the political role she wishes to play as a principled and savvy leader of the democratic left: that, whatever her intentions and the nuances of her rhetoric, her endorsement of Sanders will fuel latent and manifest acrimony between many Sanders and many Warren supporters. For the former, and especially those aligned with the official DSA position, it might be taken to mean that AOC shares the view that only Sanders is a legitimate candidate of the left worth supporting. For the latter, and especially those more mainstream Democrats who fear “socialism” and consider Warren the “safer” left candidate, it might be taken to reinforce their sense that the Sanders left cannot be trusted to support any other Democratic candidate (those so inclined will, of course, revive the acrimonies of the 2016 Hillary vs. Bernie contest).

Everything that AOC has said and done since seeking and then winning public office indicates that she is a bridge-builder on the democratic left who does not want to promote such division and who understands that at the end of the primaries it will be essential for all Democrats to come together to defeat Trump. Indeed, one of the most admirable things about AOC is that unlike some on the left who want only to talk about political economy of capitalism and who regard impeachment as a form of self-righteous liberal “tyrannophobia,” AOC has been consistent and vigorous in her critique of Trump’s authoritarianism (her DSA and House colleague Tlaib has been equally consistent and vigorous).

For this reason, AOC’s endorsement of Sanders represents both a challenge and a great opportunity for her to demonstrate real “statesmanship” (is there a gender-neutral term for this?): She needs to publicly and enthusiastically endorse Sanders in a way that also gives a real nod to Warren and that also publicly and enthusiastically states that while she considers Sanders to be the best opponent of Trump, she pledges to work hard for any Democratic presidential candidate, and hopes that all of her supporters, and all of Sanders supporters, share this commitment. Such a message could draw on the rhetoric by which the Working Families Party recently endorsed Warren, making a choice without exaggerating it and by articulating the core values of the democratic left.

If anyone can do all of this, it is Alexandria Ocasio-Cortez.

I hope that she will.