President Trump abruptly canceled his plans on Wednesday to sign a bipartisan bill aimed at improving housing affordability, upending a celebratory moment for both Democrats and Republicans who had been eager to promote the measure as evidence they were trying to bring down costs.
Just hours before a scheduled victory lap with lawmakers at the Capitol, Mr. Trump said in a social media post that he would not sign the legislation until Congress passed an unrelated law to impose new restrictions on voter identification and mail-in voting.
That bill, known as the SAVE America Act, has been stalled in the Senate, where solid Democratic opposition has prevented it from advancing past the 60-vote threshold required to overcome the filibuster. But it was hardly Mr. Trump’s only grievance: He also canceled the signing ceremony out of fury, after the Senate voted a day earlier to instruct an end to the war with Iran, according to two people familiar with the president’s decision.
Mr. Trump’s sudden move generated fierce blowback from congressional Democrats and puzzlement from a handful of Republicans, on a day when Mr. Trump joined G.O.P. senators for a highly contentious private lunch. The president lashed out at Senate Republicans at that gathering, after four of them voted to support the resolution on Iran, which he said could impede the ongoing negotiations between Washington and Tehran.
It also angered those who had worked most closely on the housing package, the byproduct of more than a year of fierce debate and compromise after decades of inaction in the nation’s capital one of the most pressing financial issues facing families.
By Wednesday afternoon, much remained uncertain about the president’s exact plans for the housing package. Mr. Trump did not say if he intended to cancel only the signing ceremony or if he would take the added step of vetoing a bill his aides had previously said he would enact.
If the president chooses only to forgo the signing, however, the measure could still become law. When Congress is in session, legislation can generally become law 10 days after a bill is enrolled and presented to the president. It was not immediately clear if the bill had been presented to the White House.
Still, Mr. Trump’s decision threatened to deprive Republicans, in particular, of an opportunity to showcase a legislative success in a year with very few of them — one that spoke directly to voters’ economic concerns. The timing of his threat only added to the awkwardness, with it arriving just as House Republican leaders were championing the housing bill during a weekly news conference.
“House Republicans are going to be the party that governs and delivers,” said Representative Tom Emmer of Minnesota, the No. 3 House Republican, seemingly unaware of Mr. Trump’s social media post.
The White House had similarly promoted the bill — the first major piece of housing legislation to be adopted in more than 30 years — and had shared an equally supportive statement about its components on Tuesday night.
But on Wednesday, Mr. Trump said the bill was “of minor importance” and that it “pales in comparison” to his preferred elections legislation. He once again urged Republicans to eliminate the filibuster to pass the elections bill, even as Senator John Thune, Republican of South Dakota and the majority leader, has said that it does not have enough support among his conference to do so.
Mr. Trump also said that the housing bill was not as crucial as “lower interest rates,” and called it “Warren centric,” along with a racial slur to refer to Senator Elizabeth Warren of Massachusetts, the top Democrat on the Banking, Housing and Urban Affairs Committee.
The White House did not respond to a request for comment.
While Mr. Trump focused on Ms. Warren’s involvement in the bill, the measure cleared both chambers with overwhelming support this week, a rarity in hyperpartisan Washington. It was the culmination of a long negotiation involving Ms. Warren and others including Senator Tim Scott, Republican of South Carolina and the chairman of the Banking Committee, and Representative French Hill, an Arkansas Republican who chairs a similar panel in the House.
The measure aims to lower housing costs by making it easier and cheaper to construct new homes. Spanning roughly 380 pages, the so-called 21st Century Road to Housing Act reduces a bevy of federal regulations and seeks to incentivize more development at the local level, adopting an approach that generally won broad support among economists and housing experts.
The measure even includes some of Mr. Trump’s own priorities, such as a new prohibition on large investors that snap up single-family homes, which the president tried to tackle in a limited executive order earlier this year.
Both parties had celebrated the bill as a way to make housing more affordable. Senator Chuck Schumer, Democrat of New York and the minority leader, accused Mr. Trump on Wednesday morning of “running away from one of the very few accomplishments that could actually help the American people.”
Some Republicans also seemed uncomfortable with the move. Senator Susan Collins of Maine, who is among the most vulnerable Republicans running for re-election this year, later called Mr. Trump’s announcement a “complete surprise.” The bill, she said, “has strong bipartisan, bicameral support.”
Yet Mr. Trump at times had been dismissive of the housing package, telling The Washington Examiner at one point in April that he was “looking at other things very strongly.”
Then, and now, Mr. Trump argued that he believed the most important force to lower housing costs would be a reduction in interest rates, which could ultimately help to push down mortgage bills. Rates on a 30-year mortgage have hovered around 6.5 percent, which has deterred some families from buying new homes and priced many out of the market altogether.
Reacting to the news, Ms. Warren sharply criticized Mr. Trump in an appearance on CNBC, saying the decision to cancel the signing “made clear that he isn’t worried about families’ rising expenses.”
“This just doesn’t make any sense, other than whatever it is he wants to do is a complete indifference to the cost squeeze on American families, and to genuine efforts to do something about it,” she added. “You know, he could be over here trying to claim a victory lap, and instead he’s saying no, no, he doesn’t want anything to do with it.”
Many of the groups that had spent months lobbying to advance the bill were apoplectic when they saw Mr. Trump’s social media post flash across their phones. Some were even en route to the Capitol, having been invited to the ceremony that the president suddenly canceled.
Sharon Wilson Géno, the president of the National Multifamily Housing Council, was on the Washington subway to the event when she received an email at 10:34 a.m. from the office of the speaker of the House, Mike Johnson of Louisiana, saying the event had been canceled because of scheduling changes.
“I guess I shouldn’t have been surprised by this. But I woke up this morning and I thought, ‘Wow, you know, this is really happening,’” she said. “So, yes, this was a big turn of events.”
Shamus Roller, the chief executive of the National Housing Law Project, was just getting up at his home in San Francisco when he saw the president’s announcement. The day before, once the bill cleared the House, he had warned his deputy to hold off on any premature celebrations.
“I said: ‘Don’t count your chickens before they hatch. Anything could happen,’” Mr. Roller said. “I don’t know if it was her bad luck or my bad luck. I don’t know what it was.”
