Washington DC - The Senate began an all-night voting session Thursday – known as a "vote-a-rama" – with Democrats expected to file hundreds of amendments to a Republican-drafted budget resolution that lacks Donald Trump's support.

Such votes are a rare moment where any senator can demand, and hold, a vote on almost any subject as an amendment to the resolution.

That means the vote-a-rama is a chance for Democrats in the Republican-controlled Senate to force vulnerable lawmakers across the aisle to take a stand on politically sensitive issues.

Republicans are willing to take such risks, however, as they try to score an early win for President Trump's legislative agenda.

US politics Kash Patel's nomination for FBI director pushed through by Senate

If successful, the process allows them to pass a budget through the Senate with just a simple majority, instead of needing 60 votes.

It would still need to pass through the second chamber of Congress – the House of Representatives, where Republicans also hold a narrow majority – before becoming law.

Senate Republicans are seeking to pass a partial budget on border security, defense, and energy as they try to notch up early political points a month into Trump's second term.

They plan to pass a second bill later to cover further budget initiatives.

But the move is at odds with Republicans in the House, who have stuck to a larger, single-bill strategy that would also extend tax cuts, among other objectives.

Trump himself has also come out against the move.

"House Resolution implements my FULL America First Agenda, EVERYTHING, not just parts of it!" he wrote in a post on his Truth Social platform on Wednesday.

Donald Trump Trump "disappointed" by Ukrainian complaints of being frozen out of US-Russia talks

"We need both Chambers to pass the House Budget to 'kickstart' the Reconciliation process, and move all of our priorities to the concept of, 'ONE BIG BEAUTIFUL BILL.'"

Senate Majority Leader John Thune had expressed surprise at Trump's post but vowed to go ahead.

"Did not see that one coming," he told reporters Wednesday, adding: "I think we're all heading in the same direction."

Some Republicans, such as Kentucky Senator Rand Paul, were also planning amendments.

"Get your popcorn," he wrote on X, formerly Twitter, ahead of the vote.