On a hot and smoky mid-July Saturday night at the Detroit Opera House, the front-running campaign in Michigan’s Senate Democratic primary had little to say about the Republican Party. But it offered no mercy for the Democratic establishment.

It was the kickoff event for Abdul El-Sayed’s biggest swing of rallies to date in what has become the country’s most-watched primary. The left-wing populist has come a long way. When he launched his campaign last year, he was speaking to small groups, and he would now be speaking to crowds in the thousands alongside the two most famous leftists in the country: Rep. Alexandria Ocasio-Cortez and the godfather of progressive insurgent campaigns, Sen. Bernie Sanders.

Sanders, 10 years out from his campaign that opened the breach between the Democratic establishment and a progressive movement that seeks to bury it, laid out the grand stakes in the Aug. 4 primary. It was no longer, he said, a race just between El-Sayed, a public health official who has never held elected office, and Rep. Haley Stevens, a moderate four-term congresswoman.

“It has now become an election of national significance,” Sanders said, and “an election of historical significance.” The outcome of the primary would “show the nation whether AIPAC and other billionaire-funded super PACs can spend tens and tens and tens of millions of dollars to buy a U.S. Senate seat.”

Over the course of the night, speaker after speaker would excoriate the Democratic establishment as beholden to corporate dollars, cynical, and out of gas. Mentions of the American Israel Public Affairs Committee or Israel would automatically provoke stray screams from attendees, who trended younger and whiter than the median Michigan Democrat. Mentions of Donald Trump would promote jeers and chuckles. But this nearly 2,000-person crowd wasn’t here to talk about Republicans. Their badness was a given. They were here to roast the rot within their own party. As the labor leader Shawn Fain, whose United Auto Workers has endorsed El-Sayed, said to the largest cheers of the night, “the only reason we’re in the position we’re in in America right now is because too many Democrats can’t decide who the fuck they want to stand with.”

Since a third candidate, state Sen. Mallory McMorrow, dropped out early in July, the Michigan Senate race has become a true instance of what so many other primaries are oversimplified as: a moderate Democrat backed by the establishment versus a progressive insurgent preaching to enthusiastic crowds.

It has gotten vicious to the point there’s concern about repairing the bridges burned along the way once whoever wins takes on the Republican in November. Well-funded super PACs—with AIPAC’s chief among them—have been doing Stevens’ dirty work of trying to take down El-Sayed, while the El-Sayed campaign is portraying the Stevens camp as corrupted by powerful interests. The raw emotions of the Israel–Palestine conflict undergird it all. Attending events from the two candidates, as I did a couple of weekends ago in Michigan, revealed two distinct factions of the Democratic Party with little in common—one trying to preserve its loosening grasp on power, the other trying to finally seize it.

I’d seen this movie before. At one point during the Detroit rally, Sanders began to make a point by saying “in all due respect to Haley Stevens,” and the very mention of her name prompted an ocean of boos. It was when Sanders waved his hand to stifle the reaction to Stevens’ name that I knew where I was—or rather, when. More than a few times a decade ago, I witnessed Sanders deploy the same gesture after offering all due respect to “Secretary Clinton.”

And, sure, Democrats had had furious battles between leading candidates before, such as Clinton and Barack Obama’s 2008 duel, but they all largely operated within the same center-left tradition. Sanders’ 2016 challenge to Hillary Clinton was different. That primary never really ended—it only mutated—and now it has arrived in Senate swing races. With polls showing El-Sayed ahead in the primary, the movement that spawned Bernie may soon have its chance to prove its theory that left populism can perform better in tight elections than the moderation offered by D.C. Democrats. After 10 years of “Bernie would’ve won” debates, we may get to test the case in Michigan.

Toward the end of her speech in Detroit, Ocasio-Cortez said that El-Sayed’s campaign “represents the politics of the future.” In the present, though, can those politics win Democrats a Senate seat they can’t afford to lose?

On the same Saturday of Abdul El-Sayed’s rally in Detroit, I met Haley Stevens at a campaign event in a small, Black-owned flower shop. I joined Stevens, the shop owner, and one other national reporter at a round table and we interviewed the congresswoman for about 20 minutes. We touched on everything from her no vote on a recent amendment to cut off military aid to Israel (“that one was way too far”) to why she considers herself more electable than El-Sayed (she’s won close races before; his only political experience is in a failed run for governor in 2018). Stevens speaks energetically in a thick regional accent. She throws every tangentially relevant piece of information she can—talking points, asides about old campaigns, recommendations for where to spend time in Detroit, references to bills she’s worked on—into each response. Occasionally, these responses address the question.

Stevens had just spent a week enduring more hostility than she usually receives from her detractors in the online left. A pep talk of hers, in which she said, “You better believe I’m going to bring it with a little bit of enthusiasm, a little bit of energy, and a little bit of stick-it-to-’em,” like an old-timey football coach, went viral and was roundly mocked online. It earned enough derision that El-Sayed put out a statement to his followers about how such comments were “unkind and unhelpful” and that if you supported him, “please stop.” (Bernie Sanders used to put out these statements when he ran against Hillary Clinton, too.)

In another familiar move, the Stevens campaign was in the process of leaning into it, with Stevens staffers showing me the box of freshly printed “STICK IT TO ‘EM” signs her team had just produced. A friend had even made it her ringtone, she told me. “But hey, whatever’s........

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