It is the former vice president, however, who is increasingly in command of the nomination fight, and so it was his forthright declaration of his intentions—with little of the usual stoke-the-drama coyness that usually surrounds such picks—that echoed in such a revealing way.

The moment showed Biden signaling that his thoughts are already far advanced into the politics of the general election. In giving up a measure of latitude about his choice, Biden also seemed to be suggesting something about how he views himself and how he wants other Democrats to view him: Not necessarily as the most commanding figure or someone clinging to personal prerogatives, but the sturdiest vessel to accommodate the party’s disparate demographic and ideological blocs.

Sturdy, in fact, seemed to be the motif for Biden’s two-hour performance, held without an audience at CNN’s Washington studio.

The last time Biden was on a debate stage was two weeks ago, in South Carolina. He was then one of six candidates on stage, with Sanders just coming off an impressive win in Nevada and threatening to take control of the race. Coronavirus was a big and looming story, but it was still days away from escalating into the all-consuming crisis that it is now. History has pivoted in those two weeks, both for Biden and the country.

That pivot imposed some new questions on Biden and Sanders both as they entered the debate.

How commanding, coherent, and credible is Biden as the race’s new frontrunner and increasingly, with House Speaker Nancy Pelosi, the most important leader of the opposition party at a moment of international emergency?

A candidate who has been uneven on debate stages and the campaign trail does not suddenly morph into Churchill. Even so, Biden opened the evening with a sober tone and factual recitation of measures he wants to fight the pandemic, including expanded testing via drive-through locations in every state, enlisting the military to help expand the pool of hospital beds, and quick action on spending to help people who have lost jobs and to offset the deadening effect on the economy.

Biden appeared more relaxed in a two-person contest, compared to earlier debates when he often receded in the noise or gave answers that bordered on unintelligible.

How many rhetorical and substantive blandishments would he offer to Sanders supporters, as he starts to unify the party?

Biden was plainly eager to propitiate progressives, offering words of praise for departed candidate Elizabeth Warren and noting that he had spoken with her this week in support of her effort to modify a bankruptcy law that Biden helped pass in 2005.

Biden’s pledge to pick a woman as running mate, though plainly planned and not spontaneous, came during a rebuttal to Sanders, who said he intended a cabinet that “will look like America,” and boasted of his superior record on abortion rights and affordable childcare for working women.

Biden said in reply that he intended to name a black women to the Supreme Court, as well as a woman to be his vice president: “There are a number of women who are qualified to be president tomorrow.”

In a notable new gesture, he said he is opposed to allowing new fracking for natural gas. Sanders wants to end even current fracking.

Still, there is a distinction between being a unifier and a sycophant. Biden repeated and at times intensified his frequent criticism of Sanders’ plans for such things as mandatory Medicare for All as too expensive and unworkable. He noted with a dig at Sanders that Italy, now suffering from widespread infection from coronavirus and a shortage of hospital beds, has government-run health care of the sort Sanders desires.

What is Sanders’ end game, now that he faces an exceedingly narrow path to the nomination?

The Vermont senator came eager to debate his ideological arguments—especially on curbing corporate power, expanding health care, and mobilizing to fight climate change—and said he worries that Biden would have problems mobilizing young people in a general election against President Donald Trump.

But he did not try to light up Biden in sharply personal ways, in the fashion that Warren did successfully against former candidate Michael Bloomberg in the two previous debates.

Instead, Sanders portrayed Biden as well-intentioned but timid. On climate change, for instance, he told Biden: “I know your heart is in the right place, but this requires dramatic, bold action. We've got to take on the fossil fuel industry. Your plan does not do that.”

This is hardly the kind of language that is impossible to walk back, or that gets in the way of an eventual endorsement, which Sanders says he will give to Biden if his own comeback plans don’t materialize.

The debate, which CNN co-sponsored with Univision, was originally supposed to be in Arizona, the Democratic National Committee decided it was irresponsible to hold it before an audience and to make so many people travel to get there. Arizona, Florida, Illinois, and Ohio vote in primaries on Tuesday.

While the debate started out with a sense of large moment because of the pandemic, before long it bogged down in sections that, given the broader context, seemed small and backward looking.

Sanders peevishly needled Biden for a decade ago backing the Bowles-Simpson budget commission, which contemplated curbing the growth in spending for Social Security, Medicare, and veterans benefits. Biden denied backing the commission, or any plans to cut popular entitlements.

“America, go to the website right now,” Sanders brayed. “Go to the YouTube right now.”

At times these crabby exchanges sounded like two old man arguing about some ancient dispute at their weekly Rotary Club luncheon.

That may well suit Biden just fine. In previous debates he often labored to break through. In this one, all he needed to do was break even. There was nothing over two hours of debate that seemed to fundamentally change the trajectory of the race, and that trajectory right now is favoring Biden.