The latest sign of discord within the Democratic Party has all the trimmings of a made-for-2020 moment: celebrity controversy, Twitter outrage, and a re-litigation of 2016.

As nearly two dozen candidates compete for the party’s nomination, tensions between two prominent Democrats—the president of a liberal think tank and co-chair of a presidential campaign—erupted into public view on Tuesday night, reopening old wounds from the last campaign that have never really healed.

The exchange started with a tweet from Neera Tanden, the president of the Center for American Progress, in response to an article that reported the mayor of Dayton, Ohio, needed extra security after President Trump insulted her following a recent mass shooting in the city.

“News like this has become commonplace and every once in a while, I just want to thank @SusanSarandon for her campaigning, not just voting, third party. Instead of working to stop Trump, she helped him,” Tanden wrote.

Tanden targeted Sarandon, an Academy Award-winning actress and surrogate for Sen. Bernie Sanders (I-VT), over her campaigning for Green Party candidate Jill Stein after Hillary Clinton defeated Sanders for the nomination in 2016.

Her tweet caught the attention of Nina Turner, the national co-chair of Sanders’ 2020 campaign, who came to the quick defense of her celebrity surrogate. “You have some nerve @neeratanden! It’s your area of expertise to start mess. Last time I checked, this is America and folks have a right to vote for who that want. Get off @SusanSarandon. She does not answer to you.”

After a tense exchange, Tanden following up by asserting a claim that Turner herself voted for Stein, who earned just 0.4 percent of the vote in the general election.

“They always blame Susan Sarandon for HRC’s loss,” Turner told The Daily Beast. “Is Susan Sarandon that fucking powerful? We don’t elect presidents by the popular vote. Is that Susan Sarandon’s fault too?”

Reached for comment by The Daily Beast, Tanden attempted to diffuse the tension from her previous comments.

“Twitter can get overheated and while I may personally disagree with Nina Turner about third party voting, I appreciate Senator Sanders’ calls in 2016 and 2020 to support the Democratic nominee, if it’s not him, as I tweeted last night,” Tanden said in a statement. “I unequivocally share that commitment, and always have. Donald Trump is an existential threat to progressive values and I remain steadfast in my view that what unites us is larger than what divides us.”

Still, while the need to defeat Trump may unite them, that hasn’t healed the lingering anger from the 2016 campaign. Democrats with ties to both Sanders and Clinton acknowledge the resentment from the last election still permeates the discussion ahead of 2020, and are hard-pressed to come up with a shared message of how to mitigate the disagreements moving forward.

“If he wasn’t running again, I don’t think it would be an issue,” one senior Democratic strategist who worked with Clinton said. “There’s a lot of feeling that Bernie really did scorched earth politics.”

Another Clinton strategist predicted Sanders will not be the nominee and took a shot at his supporters who believe he could secure the nomination, further illustrating that the rift of last cycle lives on.

“Bernie Sanders will never be the Democratic nominee for president nor will he be on the Democratic ticket for president,” Adam Parkhomenko wrote on Twitter on Wednesday. “He is not a Democrat. If you believe otherwise you are a complete fool.”

The divide among progressive and moderate Democrats has gripped Congress in recent months. House Speaker Nancy Pelosi (D-CA) and Rep. Alexandria Ocasio-Cortez (D-NY) temporarily put their ideological disagreements on hold to unite against Trump’s repeated racist attacks on several freshman congresswomen of color. When fellow progressive Reps. Rashida Tlaib (D-MI) and Ilhan Omar (D-MN), the only two Muslim women in Congress, were temporarily barred by the Israeli government from traveling to the country, Democrats again saw glimpses of unity.

But heading into 2020, as Sanders competes for the primary’s progressive lane with Sen. Elizabeth Warren (D-MA), more moderate candidates have repeatedly taken jabs at what they see as the party’s shift too far leftward. In the latest debate in Detroit, for example, four moderate Democrats launched into the types of attacks that can be weaponized by the Republican opposition.

While research indicates there is less division among Democrats than in the past on immigration and racial equality, two pillars of Trump’s re-election campaign, there is also a sizable divide within the party along broader ideological lines. A Pew Research Center study from January showed that 53 percent of registered voters who are Democrats identify as more moderate, while 40 percent say they’re more liberal.

“Where you’ll see its intensity is when voting starts,” the senior Democratic strategist said. “Really it will depend on how quickly one person is able to secure the nomination. It’s not going to be right after Iowa and New Hampshire.”