In 2015 and early 2016, the leaders of some of the United States’ major unions practically jumped over themselves to support Hillary Clinton for president. More significant than the fact of these endorsements was their timing: in many cases, they came before a single primary vote had been cast, and before the candidate herself had offered anything substantive in return.

It’s difficult, in retrospect, to argue that such endorsements achieved much of anything. Clinton would ultimately win the Democratic nomination and go on to run one of the most substance-free general election campaigns in modern history — pouring countless millions into personality-themed ads while neglecting to champion worker-friendly policies or hold events in labor settings. In Michigan, despite the Obama administration’s efforts to rescue the automotive sector, she did not visit a single UAW hall.

This series of events was certainly a case study in centrist incompetence, but it was also a study in the tactical ineffectiveness of many labor leaders’ deference toward Democratic elites. Rather than extracting guarantees or concessions from the Clinton campaign, early union endorsements, if anything, encouraged it to take labor support for granted.

The United Auto Workers’ ongoing strike has been a welcome contrast — a testament to the strategic superiority of worker militancy, rather than deference, in getting the goods. Even before the walkout began, the UAW’s newly elected reform leadership made clear it expected the self-proclaimed “most pro-labor president in history” to choose a side.

“I think our strike can reaffirm to [Biden] where the working-class people in this country stand. . . . It’s time for politicians in this country to pick a side,” UAW president Shawn Fain told CNBC’s Brian Sullivan earlier this month. “Either you stand for a billionaire class where everybody else gets left behind, or you stand for the working class.” And while Fain was openly critical of Donald Trump’s fraudulent efforts to align himself with workers, he was also clear that Biden couldn’t take his union’s approval for granted. “Our endorsements,” Fain declared, “are going to be earned, not freely given, and the actions are going to dictate who we endorse.”

Yesterday the strategic wisdom of that posture was vindicated by a historic first: a visit by a sitting president to a picket line in support of striking workers. Already Biden had put out supportive statements that in some cases directly echoed the union’s own messaging. But the UAW held firm and, facing sagging poll numbers, widespread public support for the union, and an impending visit by Donald Trump to Michigan — though, notably, not to speak to union autoworkers — Biden was successfully nudged into action. And while he ultimately spoke for less than two minutes on Tuesday, there is no denying the power or effect of a US president standing shoulder to shoulder with striking workers and declaring, as Biden did:

Wall Street didn’t build this country, the middle class built this country, and unions built the middle class! That’s a fact, so let’s keep going. You deserve what you’ve earned, and you’ve earned a hell of a lot more than you’re getting paid.

There is a clear lesson here with implications beyond the current strike action. It was worker militancy, after all — not acquiescence toward political elites — that brought a Democratic president to the picket lines. Ahead of next year’s presidential election, unions and progressive groups alike should take note and wield whatever leverage they have at their disposal. By doing just that, the UAW has demonstrated the radical potential that comes from challenging political power instead of genuflecting to it — and, in the process, has achieved something remarkable on behalf of America’s entire working class.