Some supporters of Sen. Bernie Sanders (D-Vt.) booed speakers at the Democratic National Convention in Philadelphia on July 25 – and a few Clinton fans aren't happy about it. (Peter Stevenson,Alice Li,Dalton Bennett/The Washington Post)

The possible futures of Bernie Sanders’s “political revolution” were visible across this city on Wednesday. At protests inside and outside the Democratic National Convention, the Vermont senator’s supporters bemoaned his loss of the nomination and flirted with whether — or when — to bolt the party.

“The election is not tomorrow; the election is in November,” said actress Susan Sarandon, one of Sanders’s most high-profile backers. Referring to Democratic nominee Hillary Clinton, Sarandon said, “I’m going to wait to see if she makes any shifts.”

Earlier, at a downtown LGBT center, a Socialist Caucus for members of the delegation became a debate over how to unify behind Clinton. Organizers for Democratic Socialists of America (DSA), for the Working Families Party and for the pro-Sanders union National Nurses United told hundreds of Sanders delegates that they needed to join a popular front against Republican nominee Donald Trump and not quit the Democratic Party in a pique.

“We must defeat Donald Trump and we must defeat him resoundingly,” said Bob Master, the co-chair of the Working Families Party in New York. “We don’t want to make the classic error of thinking that the liberals are our enemy. They’re not our friends, but we need them.”

The convention’s third day was the first that supporters of Sanders could no longer fantasize about how he might win the nomination.

While polls show most Sanders supporters will vote for Clinton, the holdouts have never been more visible than this week in Philadelphia.

In interviews, many said that they would continue to reflect on the choice between backing Clinton or the Green Party.

Sanders, who on Tuesday launched the first of three planned post-campaign organizations and closed the roll call of states’ votes by supporting Clinton, had temporarily stepped out of the debate.

“As of yesterday, I guess, officially, our campaign ended,” he told delegates from Maine, New Hampshire and Vermont at a Wednesday morning breakfast. “What we’re doing now is transitioning our movement.”

But while Sanders called Trump “the worst Republican candidate in the modern history of America,” he did not assume all of his supporters would support Clinton.

“We never wanted to have control of our supporters,” Sanders’s wife, Jane, told CNN. “We wanted to engage them in the political process.”

Many Sanders delegates went from disappointment to disgust as the convention moved past them. Hundreds left Wells Fargo Center after Clinton’s nomination Tuesday, and some did not return, unwilling to participate in a carefully choreographed ceremony for the nominee.

Larry Sanders, the older brother of Sen. Bernie Sanders (I-Vt.), cast his vote for his brother during the second day of the Democratic National Convention. (Victoria Walker/The Washington Post)

“They are obsessed with this forced unity stuff, and it’s totally counterproductive,” said Cenk Uygur, the host of the online news network the Young Turks. “They’d have a lot less drama if they let people hold up the signs they wanted.”

Wednesday’s major protest inside the convention perimeter was staged to support Nina Turner, a Sanders supporter from Ohio who was denied the chance to help put Sanders’s name in nomination. (She spent part of Tuesday night in Sanders’s viewing box.) Smaller than a similar Tuesday protest, the Wednesday action moved inside the Democratic convention itself, protesting former New York mayor Michael Bloomberg and former defense secretary Leon E. Panetta.

The Socialist Caucus took a different path, as movement leaders argued that not voting for Democrats in 2016 was reminiscent of the decision some Weimar Republic socialists made in allowing Adolf Hitler to take power in Germany in the hopes that it would lead to a true revolution.

“We do need a third party, eventually,” said Maria Svart, DSA’s national director. “We just don’t feel it’s viable at all right now.”

Supporters of Green Party candidate Jill Stein, who has found support at protests all week, were outnumbered in the meeting of delegates. Some activists openly scoffed at the idea that the Greens could be a vehicle for Sanders’s cause.

“We’re trying to build a mass movement, and I don’t see that happening with Jill Stein,” said Rahel Biru, a socialist activist from New York.

And there was tension in the room when one Stein supporter began cursing the idea that she had to vote for Clinton. Ashley Rodriguez, an organizer for DSA and a Sanders delegate from Texas, used that moment to make a point: The Stein voter was white, and perhaps had less to lose if Trump won the presidency.

“It’s very scary, as a Latina who lives on the border and has been the target of the racism Trump is giving voice to,” Rodriguez said. “Sometimes you need to check our privilege at the door and realize who will really be affected by your decision.”