Today President Joe Biden traveled to Detroit to join members of the United Auto Workers (UAW) on the picket line in their strike against the Big Three automakers. The move was Biden’s strongest signal of support yet, after a number of more equivocal statements about the ongoing contract dispute. He is the first sitting US president in history to walk a picket line.

Biden’s transportation secretary, Pete Buttigieg, declared that Biden went to Detroit because he is “deeply pro-worker.” One might doubt Buttigieg’s assessment, given that — despite Biden’s admirably pro-labor National Labor Relations Board — the president intervened to stop railworkers from striking over eminently reasonable demands less than a year ago and has so far been content to fund a transition to electric vehicles (EVs) with little regard for workers. (Buttigieg himself went on to qualify his statement: the president, he says, wants “the auto sector to succeed as well” and is “pushing the parties to get to a win-win deal that does right by workers.”)

In any case, to look at Biden’s decision as simply reflecting his personal commitments is to miss the bigger picture. Biden is looking toward reelection, Michigan is a crucial swing state, and the president and his team almost certainly feel a trip to the UAW picket line will be a boon to his electoral odds. And considering union favorability is at an all-time high and a majority of Americans support the UAW walkout, they’d be right to think so.

The episode illustrates a broader political effect of mass strikes. The UAW represents nearly 150,000 workers at Ford, General Motors, and Stellantis, three giant and highly profitable US corporations. With militant leadership calling out the companies and making historically ambitious demands in public, the strike is polarizing society. Many in the pundit class are harshly criticizing the striking workers: CNBC’s Jim Cramer lambasted UAW president Shawn Fain for engaging in “class warfare,” saying “I find him frightening.” The opinion pages of the Washington Post and the Wall Street Journal are full of denunciations of the strike.

As part of this general polarization, politicians across the political spectrum are being forced to pick a side. Some came out in support of UAW early and enthusiastically — Bernie Sanders was unsurprisingly among them, joining the picket line on day one of the strike, along with congresswoman and Detroit Democratic Socialists of America member Rashida Tlaib. Fellow DSA congressmembers Alexandria Ocasio-Cortez and Cori Bush have enthusiastically backed the strike as well.

The walkout has even garnered superficial support from some Republicans, including pseudopopulists Josh Hawley and J. D. Vance — though they are using the opportunity to cynically misrepresent labor as opponents of an EV transition. Other politicians have come out in defense of the auto companies, of course, including GOP presidential candidates Nikki Haley and Tim Scott; Democratic representative Elissa Slotkin of Michigan, meanwhile, offered a backhanded expression of “support” for workers while hoping the strike would be “short-lived” and urging workers to “not let the perfect be the enemy of the good.”

What’s happening right now is an exceedingly rare occurrence in US politics. Too often, political discourse revolves around politicians’ personal foibles or invented scandals, while real injustices become a topic of discussion only insofar as they serve partisan ends. (See, for instance, establishment Democrats’ flip-flopping on US immigration policy.)

We don’t often see politicians and commentators forced to choose a side in the class struggle — especially not when what’s at stake is a popular, massively visible strike by workers in a core industry, led by a union president who declares that his members are “fight[ing] for the entire working class.” Moments like this can also be enormously clarifying for millions of ordinary people who don’t normally pay attention to politics or who have become disaffected. They get to see an open fight between workers demanding basic dignity and CEOs who make tens of millions of dollars a year. And they get to see who actually stands with workers when it counts.

It was for similar reasons that so many on the Left backed Bernie Sanders’s presidential campaigns. Like UAW president Shawn Fain, Sanders calls out the power of corporations and the ultrarich and says forthrightly that workers are getting screwed. “If there is going to be class warfare in this country,” Sanders declared during his 2020 run, “it’s about time that the working class won that war.”

But presidential election campaigns come and go, and they typically culminate with people dropping their votes in a ballot box. Workplace struggles like the ongoing UAW strike, on the other hand, push workers themselves into direct confrontations with the boss. In doing so, workers can win concessions that would be unachievable through solely electoral means — and force the political class to pay attention and pick a side.

Much of America is watching what’s happening in Detroit right now, and many of them have already chosen the UAW’s side. That’s what’s really exciting — along with the possibility that the strike will inspire other workers across the economy to take up the fight themselves.