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Want to know how worried Washington was about a rail strike? Typically reliable union champions Joe Biden and Nancy Pelosi successfully rallied rank-and-file Democrats to side with railroad execs over their workers.

You read that correctly: Biden decided the broader economy was a bigger priority than 100,000 freight rail workers having any paid sick leave in their next contract. After campaigning as the most pro-union presidential candidate in history, Biden signed into law a measure that makes a rail strike illegal.

Like the auto and Wall Street bailouts, the rail-worker order is likely to be an unpopular move—but ultimately one that defines a Biden legacy as much as his green-energy agenda, his infrastructure investments, and his reboot of U.S. foreign policy in the post-Trump era. It was a tough call for the White House and for Biden personally, but one that ultimately is the kind that only gets to a President’s desk when everything else fails. It may deflate part of his political base—Biden carried union households over Trump by 14 points in 2020, and Democrats carried them by 15 points last month—but it may also sustain his governing power.

The House on Wednesday passed a bill that would force management and labor to accept a White House-negotiated deal that eight of the 12 unions at the table had already agreed to. (The remaining four, however, represent more than half of the nation’s unionized freight rail workers.) On Thursday, under pressure from the White House and Wall Street alike, the Senate followed. And by Friday afternoon, Biden was in the Roosevelt Room of the White House to sign a deal that leveraged the government’s power to keep workers on the job if they are linked to interstate commerce.

“I know this was a tough vote for members of both parties,” Biden said on Friday. “It was tough for me.”

For sure there were sacrifices. A companion proposal that would have introduced sick leave for workers was cleaved from the package and died in the Senate, another blow to union members.

“We’re going to avoid the rail strike, keep the rails running, keep things moving, and I’m going to go back and we’re going to get paid leave, not just for rail workers, but for all workers,” Biden said at a news conference on Thursday.

With Republicans set to take control of the House come January and Washington’s urgent must-do list finding fewer and fewer hours ahead of the holiday recess, it’s not entirely clear how Biden might get any federal guarantee of paid time off through Congress.

The White House-brokered deal still has plenty for workers to embrace, including a roughly 24% pay increase by 2024 and a ratification bonus of $11,000. Still, the contract guarantees just one paid personal day off and no dedicated sick days, although there is some flexibility to step out for doctor appointments.

The quick fall of dominos stands as a reminder that, when it has to, Washington can set aside pettiness and summon unity and might to avoid a crisis. The rail workers had eyed Dec. 9 as a potential start to a strike, a protest that could have sent the whole economy into a crippling recession and cost as many as 750,000 jobs, according to one estimate. Another scary figure: a rail strike could cost the broader economy $2 billion per day.

Biden, who calls himself “Union Joe” in front of friendly union crowds, had the option of standing in solidarity with the freight workers—and, symbolically, all members of the labor movement—or steering the locomotive onto safer tracks. The choice was hardly an appealing one, but this is why voters opted for Biden in 2020—the promise of steadier leadership. Biden’s calculation was that his longtime pals will understand the terrible choice he faced and accept why he did what he did.

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