Shortly after one o’clock in the afternoon on Tuesday, young staffers on Capitol Hill were sent by their bosses to the graphics offices so they could print out an X post from Elon Musk. The recently departed advisor to President Trump had called the One Big Beautiful Bill Act an “abomination,” and Democrats were suddenly having their best day in months. 

The post came as Republican and Democratic senators were having their respective weekly lunches with their colleagues. Minutes after the post went out, Senator Schumer came to the podium in the Ohio Clock corridor just off the Senate floor with a large grin on his face. It was the happiest Mr. Schumer had seemed since losing his majority leader position last year. 

“Well, I hear something happened while we were at lunch,” he said in a cheery tone. “Which led me to make some news here today and say something I didn’t think was imaginable: I agree with Elon Musk.” 

Immediately after, he held up a posterboard printout of Mr. Musk’s missive against the budget bill, in which he described the legislation as “outrageous” and a “disgusting abomination.” 

“Shame on those who voted for it,” the world’s richest man wrote. 

Hours later, the House minority leader, Congressman Hakeem Jeffries, held his own solo press conference in the basement of the Capitol. He also took the podium with a grin on his face, and his printout of Mr. Musk’s X post was much larger than Mr. Schumer’s. 

“Breaking news: Elon Muck and I agree with each other,” Mr. Jeffries said with a smile, barely containing this new messaging weapon that had been suddenly handed to him. “The GOP tax scam is a disgusting abomination. Every single Republican who voted for the one big ugly bill should be ashamed of themselves.”

In total, Mr. Jeffries spoke for nearly 30 minutes and took more than a dozen questions from members of the press corps — a rare thing for a party leader in the House. 

Both Messrs. Schumer and Jeffries have faced fierce criticism from their own colleagues privately as well as activists in the party for failing to meet the moment in standing up to Mr. Trump. The Senate minority leader’s favorable rating among fellow Democrats crumbled after he voted to keep the government open in March, and Mr. Jeffries has been criticized for not honing a clear enough message to attack Republicans. 

It was immediately clear, however, that Mr. Musk had given them an out. The billionaire has criticized some of the actions of congressional Republicans before, though this was the most serious broadside yet. Speaker Johnson has long tried to assure reporters that all is well with the former DOGE chief who often spouts off on social media. On Tuesday, the speaker did not hold back. 

“Let me say this — It’s very disappointing,” the speaker told reporters on Tuesday. “He’s done a lot of great work. With all due respect, my friend Elon is terribly wrong about the one big beautiful bill.”

Countless Democrats in Congress reposted the message, mocking Republicans for their sudden split with Mr. Musk. “Big Bloated aBomination,” Congressman Jared Moskowitz wrote. “Hey @elonmusk, the only people who voted for this bill were House Republicans,” Congressman Robert Garcia said. 

“I haven’t agreed with Elon on much lately but …,” Senator Kelly — whom Mr. Musk once called “a traitor” — said in response to his post. 

Even some Republicans were trying to cozy up to Mr. Musk in the wake of his bombshell post, even though they themselves voted for the measure. 

“So @elonmusk is right to call out House Leadership. I wish I had a nickel for every time the @freedomcaucus sounded the alarm and nobody listened, only to find out the hard way we were right all along,” a former Freedom Caucus chairman, Congressman Scott Perry — who voted for the bill last month — wrote on X. “We expect MASSIVE improvements from the Senate.”