A fierce political battle erupted on Capitol Hill Monday as Senate Republicans defended a controversial plan to funnel $1 billion into security tied to President Trump’s proposed White House ballroom project, triggering outrage from Democrats who accuse the G.O.P. of prioritizing a “palace” over struggling Americans.

The clash comes as Republicans race to push through a massive $71.7 billion spending package aimed at supercharging the administration’s immigration crackdown before June 1. But instead of focusing solely on border enforcement, the bill has ignited a storm over funding linked to Trump’s lavish ballroom vision, a project already facing growing public backlash.

Democrats are now seizing on the controversy as a potential election-year weapon.

“This is exactly the kind of thing voters remember,” one Democratic aide said privately Monday as lawmakers returned to Washington for the first major fight over the legislation.

Republicans Say It’s About Security, Not Luxury

Top Senate Republicans insisted the money is not intended to build the ballroom itself, but rather to strengthen security protections around the president amid escalating threats.

“It is a security-related measure,” said Senator John Thune, Republican of South Dakota and the majority leader, who noted the three assassination attempts against Mr. Trump in the past two years. “Obviously the money that’s in there is about securing that building. Secret Service has a job to defend and protect the president, and I need to make sure they have the tools to do it.”

Trump has repeatedly said the ballroom, which he estimates will cost roughly $400 million, would be funded through private donations. Still, some Republicans have openly pushed for taxpayer money to support the project.

The issue has quickly become politically explosive.

Senator Charles E. Grassley, the Iowa Republican who chairs the Judiciary Committee, argued that mounting global events and recent security scares justify the spending surge.

“We’ve got to beef up the Secret Service,” said Mr. Grassley, whose panel is responsible for the majority of the funding request.

Grassley pointed to upcoming events like the World Cup and the attempted attack at the recent gala for White House journalists as examples of growing security risks facing federal officials and public gatherings.

Democrats Unleash “Ballroom Republicans” Attack

Democrats wasted little time turning the ballroom funding into a symbol of what they call Republican excess and misplaced priorities during a time of economic pain for many Americans.

“Their billion-dollar bill has zero dollars to help Americans deal with groceries and gas prices going up, zero dollars to bring down Americans’ health care, housing and electricity bills,” Senator Chuck Schumer of New York, the Democratic minority leader, said on the Senate floor on Monday. “At a time when Americans are struggling to put food on the table, Republicans say ‘Let them eat cake,’ and demand American taxpayers build Trump a palace while they are at it.”

Behind the scenes, Democrats are preparing to hammer Republicans relentlessly on the issue heading into the election season.

In a sharply worded letter to Democratic colleagues, Schumer branded the Senate majority “Ballroom Republicans” and vowed to “force vote after vote” targeting what he described as “Trump’s gaudy ballroom.”

Polls have reportedly shown the ballroom project is unpopular with voters, giving Democrats fresh ammunition as inflation and consumer costs remain major concerns nationwide.

Immigration Crackdown Bill Faces High-Stakes Fight

The broader legislation would provide massive new funding for Immigration and Customs Enforcement and Customs and Border Protection for the remainder of Trump’s term.

Democrats refused to support additional funding for those agencies unless Republicans agreed to changes in immigration enforcement practices, including restrictions on ICE officers covering their faces during operations.

Republicans are now relying on a special budget process designed to bypass a Senate filibuster and avoid Democratic obstruction.

The aggressive timeline underscores how critical the legislation is to the administration’s immigration agenda.

Mr. Thune said Republicans have invited the head of the Secret Service, Sean M. Curran, to a private party luncheon in the Capitol on Tuesday to explain exactly how the security funding would be used.

Even Some Republicans Are Raising Questions

Not every Republican appears fully comfortable with the proposal.

“I will be following it very closely to see what the justification is for increased security at the White House,” Senator Susan Collins, the Maine Republican in a tough re-election fight, told reporters in Maine late last week. “There, I believe, is a plan for a bunker to be built underneath the ballroom and that may make sense,” she said, adding that she believed the ballroom itself should not be built with federal funds.

Other Republicans have gone even further in support of the project.

Senator Lindsey Graham, the South Carolina Republican who chairs the Budget Committee, has called for Congress to directly approve federal money for the ballroom itself.

The sudden inclusion of the White House security funding reportedly surprised some lawmakers because Republican leaders had originally tried to keep the legislation narrowly focused on immigration enforcement to improve its chances of fast passage through the narrowly divided House.

Still, Thune insisted the funding belongs in the package.

“I think it fits nicely within a package that is built around basically public safety, whether it’s at the border, on our streets, in our neighborhoods, in our communities — and in this case, it’s protecting the president,” he said.

Democrats Escalate Attacks Over ICE Policies

As the debate intensified, Democrats also blasted Republicans for trying to fund the immigration crackdown outside normal government spending negotiations.

They argued the maneuver was necessary only because the administration refused to compromise on oversight measures involving ICE officers.

“ICE continues to argue it is the only police force in America that should be masked and the American people shouldn’t be able to identify who these ICE agents are,” Senator Richard J. Durbin of Illinois, the No. 2 Senate Democrat, said. “I think that’s reprehensible. We are trying to change it and the Republicans are resisting it.”

With Republicans pressing to pass the bill before June 1 and Democrats preparing a full-scale political assault, the battle over Trump’s ballroom security funding is rapidly becoming one of the most combustible fights in Washington.