There was no clear path out of the impasse, while agencies warned that the 15th government shutdown since 1981 would halt the release of a closely watched September employment report, slow air travel, suspend scientific research, withhold pay from U.S. troops and lead to the furlough of 750,000 federal workers at a daily cost of $400 million.
Trump, whose campaign to radically reshape the federal government is already on track to push out some 300,000 workers by December, warned congressional Democrats that a shutdown could clear the path for "irreversible" actions including cutting more jobs and programs.
The shutdown commenced hours after the Senate rejected a short-term spending measure that would have kept government operations afloat through November 21.
Democrats opposed the legislation over Republicans' refusal to attach an extension of health benefits for millions of Americans that are due to expire at the end of the year. Republicans say the issue must be addressed separately.
At issue on the government funding front is $1.7 trillion for agency operations, which amounts to roughly one-quarter of the government's total $7 trillion budget. Much of the remainder goes to health and retirement programs and interest payments on the growing $37.5 trillion debt.
Independent analysts warn the shutdown could last longer than the budget-related closures of the past, with Trump and White House officials threatening to punish Democrats with cuts to government programs and the federal payroll.
Trump budget director Russell Vought, who has called for "less bipartisan" appropriations, threatened permanent layoffs last week in the event of a shutdown.
RECORD DATES TO FIRST TRUMP TERM
The longest government shutdown in U.S. history stretched over 35 days during December 2018 and January 2019 during Trump's first term in office, in a dispute over border security.
"All they want to do is try to bully us. And they're not going to succeed," Senate Democratic leader Chuck Schumer said in a floor speech a day after a White House meeting with Trump and other congressional leaders that ended with the two parties far apart.
Senate Majority Leader John Thune described the failed short-term spending bill as a "nonpartisan" measure devoid of partisan policy riders that Democrats have had no problem accepting in years past.
"What's changed is, President Trump is in the White House. That's what this is about. This is politics. And there isn't any substantive reason why there ought to be a government shutdown," the South Dakota Republican told reporters.
Trump's Republicans hold majorities in both chambers of Congress, but legislative rules require 60 of the 100 senators to agree on spending legislation. That means that at least seven Democrats are needed to pass a funding bill.
DEMOCRATS FOCUS ON HEALTHCARE FUNDING
Democrats are under pressure from their frustrated supporters to score a rare victory ahead of the 2026 midterm elections that will determine control of Congress for the final two years of Trump's term.
The healthcare push has given them a chance to unite behind an issue that resonates with voters.
Along with the extended health subsidies, Democrats have also sought to ensure that Trump will not be able to undo those changes if they are signed into law. Trump has refused to spend billions of dollars approved by Congress, prompting some Democrats to question why they should vote for any spending legislation at all.
University of Chicago professor Robert Pape said the unusually polarized U.S. political climate in the aftermath of conservative activist Charlie Kirk's assassination and the growing power on the extreme wings of both parties could make it harder for party leaders to agree on a deal to reopen the government.
"The rules of politics are radically changing and we can't know for sure where all of this is going to end," said University of Chicago political science professor Robert Pape, who studies political violence.
"Each side would have to backtrack against tens of millions of truly aggressive supporters, their own constituents, which is going to be really hard for them to do," he said.
Before the shutdown, Trump reached out to his own supporters with a deepfake video showing manipulated images of Schumer appearing to criticize Democrats while top House Democrat Hakeem Jeffries stood next to him, with a crudely drawn sombrero and mustache imposed over his face.
"It was childish. It was petty," Schumer told reporters. "It's something that a 5-year-old would do, not a president of the United States. But it shows how unserious they are. They don't give a damn about the harm they will cause with their shutdown."
