On Thursday night, nearly a thousand people, largely Democrats, stormed a town hall in Utah where Rep. Jason Chaffetz, the Republican chair of the House Oversight Committee, was convening with his constituents. Upset that Chaffetz would not commit to investigating Donald Trump’s financial conflicts of interest, that he has supported Trump’s executive orders, and that he had lobbied the president to open a newly designated national park to private commercial use, they yelled and jeered, drowning out the congressman’s attempts to respond to questions.

Chaffetz’s attempts to assuage the crowd fell flat. “You’re really not gonna like this part,” he said at one point. “The president, under the law, is exempt from the conflict-of-interest laws.” He then left the town hall 40 minutes early, drawing boos and chants of “We’ll be back!”

The phenomenon hasn’t been limited to Chaffetz: across the country, Republican representatives holding meetings in their home districts have been flooded with liberal, Democratic activists protesting their political ties to Donald Trump. The grass-roots movement, once limited to eager volunteers canvassing through swing states and phone banking, has suddenly grown more confrontational, galvanized by outrage over the new administration, with constituents flooding their representatives’ inboxes, and protesting—loudly—wherever their lawmakers go. Some Republican legislators are even beginning to take security precautions at public events.

The explosion of Democratic discontent, pegged in part to the unraveling of Obamacare, evokes an obvious parallel with the birth of the Tea Party, itself fueled in part by distress over the U.S. health care system. Now, approximately seven years after the Republican Party faced an insurgent uprising within its ranks, Democrats are confronting the beginnings of their own civil war between the party’s well-heeled establishment and its restless, grass-roots base. Some within the party have accused the pro-Obama group Obama for America of taking too large a role in state-level organizing, undermining local efforts. “OFA had no faith or confidence in the state parties, so they created a whole separate organization. They took money away and centralized it in D.C.,” Nebraska Democratic Party Chair Jane Kleeb told Politico, calling on the organization to shut down. “They gave us a great president for eight years, but we lost everywhere else.” That strain of bottom-up discontent has crept into the race for the chairmanship of the Democratic National Committee, too, where longtime Obama ally Tom Perez is fending off a challenge from the progressive Keith Ellison. House Minority Leader Nancy Pelosi was also forced to tamp down rebellion within her ranks when the populist Rep. Tim Ryan launched a bid to oust her. Ryan’s effort failed, but it highlighted the desire among some within the party to install a more blue-collar voice atop the congressional hierarchy.

In the meantime, the orientation of the Democratic Party in Washington has turned decidedly leftward, and increasingly antagonistic, as lawmakers adjust to a new political reality under Donald Trump, where mass protests among the liberal base are quickly becoming de rigueur. While Democratic leadership, led by Senator Chuck Schumer, initially telegraphed its openness to working with the Trump administration on infrastructure and other potentially bipartisan initiatives, cross-aisle cooperation has quickly taken on the taint of collaboration. Taking their cues from the an increasingly energized base, Democratic senators have now voted nearly unanimously on three occasions to reject Trump’s Cabinet nominees—Attorney General Jeff Sessions, Education Secretary Betsy DeVos, and Health and Human Services Secretary Tom Price. Trump’s nominee to lead the Treasury Department, Steve Mnuchin, is expected to receive a similarly icy reception when his confirmation vote comes before the Senate on Monday.

In their quick move to the left, Democrats have surely learned a lesson from Republicans, who saw many among their ranks purged in a series of contentious primaries in 2010 and 2012, during which several high-profile, establishment stalwarts were deposed amid a wave of Tea Party upstarts. (Eric Cantor, the former House minority whip who was blindsided by economics professor Dave Brat, remains the quintessential cautionary tale.) So far, the possibility of primary fights remains little more than a threat on the left, designed to keep lawmakers in line. Either way, the party’s ideological center is on the move. The only question is whether Democrats in Congress will take the lead in the burgeoning opposition movement or find themselves left behind.