The first shots in the Democratic civil war have been fired. This month, the Democratic Congressional Campaign Committee, whose only job is to elect Democrats and protect vulnerable incumbents whatever their ideological proclivities, announced that it would withhold support for firms that work with progressive primary challengers. The insurgent progressive wing of the Democratic Party responded by engaging in open revolt.

Rep. Alexandria Ocasio-Cortez, a successful usurper herself, told her millions of followers to withhold their donations to the DCCC and instead contribute to her fellow progressives, some of whom also unseated incumbents in a primary. Progressives in Congress are already joining with activists to create organizations dedicated to imposing ideological orthodoxy on the party and ousting anyone who resists. The internecine conflict has begun to derail the Democratic agenda, as the party splits over two competing climate-change bills as the party’s signature piece of legislation—deemed H.R. 1 to convey its urgency—recedes into the background.

House Speaker Nancy Pelosi is nearing what the New York Times described as “open warfare” with the resurgent progressives she tried to appease. Former President Barack Obama is urging his fellow Democrats to avoid “shooting at your allies because one of them is straying from purity on the issues.” You could be mistaken for thinking that Democrats were in the throes of an internal struggle for ideological primacy not unlike what the Republican Party experienced amid the rise of the Tea Party. But that cannot be. After all, so many liberal ideologues and political scientists repeatedly assured us that the Democratic Party was all but immune to the Tea Party contagion.

The notion that America’s center-left party was simply too organizationally competent, pragmatic, and adaptable to engage in ideologically fratricidal politics emerged alongside the Tea Party’s inception in 2009 and 2010. It was essential to the theory of “asymmetric polarization,” postulated by Brookings Institution scholar Thomas Mann and American Enterprise Institute’s Norm Ornstein. The theory posited that conservatives had radicalized in the early part of this decade while their liberal counterparts had not, owing not to the Democratic Party’s command of the White House but some preternatural Democratic ability to resist the temptations of radicalism.

Even as grassroots Democrats became increasingly frustrated by their more centrist elements, and amid the rise of progressive scions like Sen. Elizabeth Warren and New York City Mayor Bill de Blasio in 2012 and 2013 respectively, the political commentariat insisted that there was no comparison between the right and left. “The Democrats’ liberal faction has been greatly overestimated by pundits who mistake noisiness for clout or assume that the left functions like the right,” wrote the Atlantic’s Molly Ball in 2014. Democrats with whom she spoke insisted that there was almost no disagreement within the party on a range of economic, social, and cultural issues. “The fact is,” she added, “the parties are asymmetrical.” There were just too few self-identified liberals to have the kind of authority that conservatives wielded over the GOP.

In 2015, Bernie Sanders’s surprisingly potent presidential campaign led a few liberals to wonder if their self-congratulatory posture was ill-considered. That wonder was fleeting. Sure, Sanders-style populists were running for and winning Democratic presidential nominations up and down the ballot, but it couldn’t last. “The four political scientists I interviewed for this story all predicted that any momentum for a ‘Bernie Congress’ would dissipate,” wrote Vox.com’s Jeff Stein in 2015. Without his presidential candidacy, “the forces Sanders conjured for the primary would scatter.”

But they did not. Following Hillary Clinton’s loss, progressive outlets began to demand a Tea Party-style ideological revolution within the Democratic Party. Even still, the party’s luminaries whistled along. “We don’t have a party orthodoxy,” Nancy Pelosi insisted in early 2017 when asked if she anticipated a rebellion on her left flank. Of the GOP, she added, “They are ideological.” Pelosi’s view reflected not just the conventional wisdom of the blogging community and the activist class but that of the academy as well.

“The lack of a ‘liberal Tea Party’ reflects a fundamental and longstanding asymmetry between Republicans and Democrats,” read the April 2018 New York Times op-ed by political scientists Matt Grossmann and David Hopkins. “The Republican Party is the agent of an ideological movement,” they continued. As such, control of the GOP had become a prize sought by a series of interest and advocacy groups, personalities, and special interests. “Democratic voters tend to view politics as an arena of intergroup competition rather than a battlefield for opposing philosophies,” these two associate professors offered by way of contrast. “Tensions within the party coalition have eased over time—to the benefit of Democratic leaders, who are now better able to satisfy the various demands of their members and avoid facing a mutiny from within.” So much for that.

Even on the eve of 2019, self-satisfaction masquerading as analysis held fast to the notion that Democrats existed outside the force of history. There could never be a “tea party of the left,” wrote Washington Post opinion writer Paul Waldman in November of last year, because “These are people who believe in government.” As such, there would never be a bloc of votes within the Democratic Caucus with the capacity to derail leadership, as the House Freedom Caucus so frequently did. Except that’s precisely what happened when an effort to condemn the anti-Semitism evinced by Rep. Ilhan Omar collapsed amid opposition by the House Progressive Caucus and the Congressional Black Caucus.

The Tea Party was conceived as an effort to thwart legislative progress, wrote the Associated Press’s Lisa Mascaro, behavior quite unlike that of Democrats. “They like government. And governing,” she wrote in December of 2018 in a profile of the Democratic Party’s legislative agenda that has been summarily overshadowed by the star power of the party’s progressive freshmen class.

Barack Obama saw this coming, even if his devoted followers refused to accept their own fallibility. As he prepared to relinquish control of the Democratic Party in 2016, the president warned Democrats not to “cannibalize our own,” to turn against incrementalism in favor of radical change, and, in the process, “stake out positions so extreme, they alienate the broad public.” In his absence, the vacuum of leadership within the Democratic Party has yielded precisely the same conditions that led to the rise of the conservative correction in 2009-2010: introspection, iconoclasm, and a succession struggle that manifests in boutique issue sets culminating in ideological purity tests.

Throughout this decade, the same conditions that led to an increase in partisanship and ideological competition among Republicans were at work on Democrats. The only distinction between Democrats and Republicans for most of this decade was control of the White House. When Democrats and Republicans traded control of the executive branch, they also swapped incentives structures. That makes logical sense, even if it doesn’t do much to make Democrats feel special.