Dianne Feinstein has been a U.S. Senator from California for longer than frappucino has been a beverage or Jurassic Park has been a movie franchise. While it’s an understatement to say she’s never been beloved, she can usually count on being able to command respect.

Among her other accomplishments, Feinstein authored the only assault-weapons ban ever to become federal law, even though it expired in 2004. She’s done a tenacious job of trying to keep the Senate’s Russiagate investigation on track against the odds. And she just failed to win her own party’s endorsement for a sixth term at the state Democratic convention in San Diego, held last week.

Nobody else reached the required 60 percent threshold for an endorsement, either. But Feinstein’s main rival, Kevin de Leon, came close, gaining 54 percent to the delegates to her 37. True, de Leon isn’t exactly a nobody, since he’s the president pro tempore of the state Senate. But he’s hardly a household name to most Californians, let alone anywhere else. His near win was plainly a rejection of Feinstein—not the result of any special excitement about de Leon himself.

Considering that California is the bluest blue state of them all, this wasn’t an insignificant rumble of discontent. Feinstein may prevail in June 5’s primary anyway, but she’s been put on notice that her brand of conventional-wisdom centrism is out of sync with party activists’ priorities. Her age—she’ll turn 85 in June—is no asset either, since the tectonic shift now underway within the Democratic Party is generational as well as ideological.

From 77-year-old Nancy Pelosi to a relative spring chicken like 67-year-old Chuck Schumer, the sight of the same familiar faces conducting what looks a lot like politics as usual has zero appeal to the hordes of fresh-to-the-cause progressives who’ve been energized—and radicalized—by their aversion to Donald J. Trump’s regime. Shambling, white-suprematist kleptocracies have a way of doing that to people, even minus a front man this humanly appalling.

The party hasn’t faced a genuine reckoning with what it’s supposed to stand for since 1972.

More than any other factor, Trump’s unpopularity is the reason Democrats are licking their lips at their chances of taking back the House (and possibly the Senate) come November. To get there, however, they’ve got to wade through what’s shaping up as an awfully messy primary season—one likely to pit a constituency of passionate newbies in no mood for compromise against Democratic clock-punchers alarmed that these upstarts will drag the party too far into extremism.

That’s basically the same tug of war the Tea Party won on the Republican side of the aisle in the 2010 midterms. As we’ve all learned since then, that kind of short-term victory can generate chaos down the road, which is why today’s GOP—despite effectively controlling all three branches of government in Washington, not to mention many states—doesn’t look like a very sustainable model for electoral success in the long run. Professional politicians dislike few things more than they dislike zealots who want to wrestle for the “soul” of a political party, because that’s a more or less meaningless concept to them. In their preferred world, parties are utilitarian devices designed to keep them in office, not referendums on ideological purity.

One of the things the pros do dislike more, though, is the kind of adamant voter who can’t be counted on to give two hoots about docilely pulling the D or R lever once his or her agenda is thwarted. Yet that describes many of the younger, alienated voters who the Democrats now urgently need to corral or, at any rate, placate. Millennials may lean liberal, but almost three-quarters of them preferred a notional third party to either existing one in one poll last fall. Stats like that can’t be good news to the Democratic National Committee’s apparatchiks.

Another complication is that nearly all of the potential candidates for the 2020 Democratic nomination are targeting the same constituency, which means that even the most mainstream of them are skewing farther left than any crop of White House contenders in decades. That can’t be good news to the DNC’s apparatchiks, either. As Bernie Sanders’s base discovered to its collective and naïve fury, the institutional Democratic party doesn’t have much sympathy for insurgents who push troublemaking ideas like free college and single-payer health care. But both of those policy planks are rapidly becoming mandatory to progressives sizing up the 2020 field. And for the first time in a generation, there isn’t an Establishment pick in sight.

Unsurprisingly, the institutional pushback against all this unruliness has already begun, including dire warnings that the Democrats had better get their act together and quash internal turmoil pronto unless they want to live up to their legend for blowing a sure thing. Marquette University political science professor Julia Azari has become one of the Establishment’s more prominent Chicken Littles, warning Vox readers that “Political amateurism presents a threat to democracy” and co-authoring a New York Times op-ed with fellow academic Seth Masket about the perils of what happens “when a party insists on being too democratic.” Translation: will all you pissed-off kids, Pussy Hat-wearing #MeToo’ers, and unreconstructed Sanders stick-in-the-muds just settle down, vote right and let the grownups do the thinking for you?

It’s not as if there aren’t real downsides to the intramural infighting, which will almost certainly get more truculent this spring, if not right up through November 6th. But the downsides of pretending that the Democratic Party can keep bumbling along without doing squat to accomodate its newly intransigent, post-Clintonite progressive wing are arguably worse. The party hasn’t faced a genuine reckoning with what it’s supposed to stand for since George McGovern’s presidential campaign went down in flames in 1972, and a tussle that’s both ideological and generational could end up as the kind of donnybrook that renews as much as it destroys.

If that means bidding goodbye to Dianne Feinstein, too bad. But she’s never been the kind of politician whose setbacks people shed tears over, and that kind of politician is what liberals are pining for these days.