Bernie Sanders has proven he can fill a stadium with adoring fans, but Democrats say he risks being ostracized by members of his own party when he returns to the Senate unless he can rein in his supporters soon.

While Sanders’s young and energetic base is something the Democratic Party desperately wants to co-opt in the general election, senior Democrats want Vermont’s junior senator to harness that anger and point it at Donald Trump. Anything less, they say, and Sanders risks coming back to the Senate alienated from his colleagues.

The violence that erupted at the Democratic convention in Nevada last weekend, with chairs being thrown, followed up by threats of violence and vulgar, sexist insults being hurled at Democratic leaders by ardent Sanders supporters, was a wake-up call for many in the Democratic Party.

California Sen. Barbara Boxer was at the mic for Hillary Clinton when the now infamous convention erupted. She’s a four-term senator, who defeated former Hewlett-Packard CEO Carly Fiorina in her last reelection, so she’s not Pollyannaish. Still, she says when she talked to Sanders on Tuesday she told him to never let his supporters do that again.

“I told him that what happened to me was very alarming, disturbing and that he needed to really get control of the situation,” Sen. Boxer told The Daily Beast. “He said he was distressed about it and expressed chagrin about it.”

Later, when Sanders sent out a press release on the affair, he doubled down, accusing the Nevada Democratic Party of being in the pro-Hillary camp. Democrats in the Senate didn’t like the sound of that, because they think it’s time for the party to heal, not throw more blows.

“I don’t think it strengthens democracy or it reflects well on the Democratic Party for us to stoop to the level of Mr. Trump, who has made this presidential campaign in his party all about needlessly, personal attacks,” said Sen. Chris Coons (D-DE).

When asked by The Daily Beast whether Sanders will be ostracized by his Democratic colleagues when he returns to the Senate if the primary ends bitterly, Coons matter of factly told The Daily Beast, “Yes.”

When asked if Sanders risked alienating his fellow senators if the vitriol continues to rise, he again responded, “Yes.”

“I think there’s been a lot of conversations in the last few days from senators here who are close to Senator Sanders or who support him or have worked with him that they’re concerned about the tone and direction and they want to make sure Nevada is an isolated, one-time incident,” Coons said.

Other Democrats are highlighting that Sanders, much like Trump on the Republican side of the aisle, is a new addition to the party. They say they let him into their exclusive playground and that a rule for admission is no sand throwing from him or his supporters.

“You know he’s been an Independent, we welcomed him, but now that he’s finally gotten around to becoming a member of the Democratic Party, you sign up for the rules and we want Bernie to go by the rules that he’s signed up for,” Sen. Barbara Mikulski (D-MD) told The Daily Beast. “That is up to him, to get his supporters to calm down. Bernie has to be in charge of what he, himself has unleashed.”

California’s senior senator, Dianne Feinstein, has raised red flags about the 2016 Democratic Convention being a repeat of the fireworks that erupted at the infamous 1968 convention in Chicago. “Party unity is always a concern,” Sen. Feinstein told The Daily Beast. “You never know. There’s a certain unpredictability that’s out there, so you need to have as solid of a united front as you can, essentially.”

But Sanders supporters in Congress accuse Clinton backers, like Feinstein, of waving red flags as an attempt to stoke “alarmist” fear.

“The only way something [like] that can happen is for the leadership, as they did in 1968, is to close off the convention to other people that were trying to change the system,” Rep. Raul Grijalva (D-AZ) told The Daily Beast.

He’s a proud progressive and an early Sanders supporter who, like many of Sanders’s most fervent people on the ground, thinks the whole primary has been tilted in Clinton’s favor. Grijalva argued the party now owes Sanders when they reach the convention floor in Philadelphia. “It behooves the party and its leadership and the DNC to treat Bernie’s ideas, his message and his people with respect, because they’ve earned it.

“You know, come on, there’s no innocence in this process. The DNC and the party itself has given aid and comfort to Hillary from the beginning. The state party, certainly in my state and other states, have supported her openly,” Grijalva said, adding that he wants his party to rewrite their rules that allow the primary to be tilted by superdelegates.

To heal the party, Grijalva also wants Clinton’s people to give Sanders and his allies a lot of time on the convention floor and to have a big say in writing the party platform. But other Sanders supporters argue the legacy of Bernie can be a lot more powerful than just a big seat at the July convention. They want a lasting legacy.

“I think the most important thing about the Sanders campaign is that, no matter what happens at the convention, that there be some sort of organization that encourages people to run for local offices all over the country in a Bernie style,” Rep. Keith Ellison (D-MN) told The Daily Beast.

Ellison envisions the new apparatus as connecting candidates who agree with the populist economic program being laid out by Sanders with his long list of small-dollar donors spread across the nation.

It’d be like the digitally progressive Obama for America, which came with the promise of helping bolster Democrats down ticket, but “only real,” Ellison told The Daily Beast.

It’s only through a nationwide network, the Minnesota congressman argued, that Sanders’s revolutionary vision for the country can be realized.

“That’s the thing that’s going to really change this country,” Ellison said off the House floor. “One of the things that Bernie has said time and time again is that no one president can change this whole country, you’re going to need a wave of people to really make the substantive changes that are necessary to really put the American democracy back in the hands of the American people.”

Other Democrats agree that Sanders will play a larger, even outsized, role in the Senate when he returns.

“He had a big role in our caucus before and it’s going to be even bigger when he comes back. He’s gonna bring back to the caucus with him a national network of progressives that’s unparalleled,” Sen. Chris Murphy (D-CT) told The Daily Beast. “I’m excited for Bernie to come back to the caucus, I’m excited for the people who got involved in his campaign to be a part of pushing his agenda.”

Murphy argues it would be good for Sanders to come back and, if Democrats can recapture control of the Senate, represent the party as the Chairman of Budget Committee.

“That would be a super platform for him to talk about the need to scale up, rather than scale down, Social Security. It would be a great platform for him to talk about democratic principles around the idea of reducing the cost of college and prescription medicine,” Murphy said. “For his Independent label Bernie has always been a pretty good member of the caucus.”

But senators from Sanders’s new party, the Democratic Party, are reticent to usher him back as a party representative unless he tones it down in these waning weeks of the primary. Still, Sanders now has a national following and cash cow of a small-dollar fundraising network, which means he’s well prepared to make life Hell for Democratic leaders unless they concede and cave to some of his supporters’ demands.

“This is a pretty incredible institution where any senator, at any time, can become pretty relevant,” Sen. Ben Cardin (D-MD) told The Daily Beast. “So Senator Sanders has always been a pretty effective member of the Senate and I assume he will continue to be.”