Booker took to the Senate floor on Monday evening saying he would remain there as long as he was “physically able.” The 55-year-old senator was plainly exhausted Tuesday morning as his speech stretched into its 16th hour. It was a remarkable show of stamina — among the longest in Senate history — as Democrats try to show their frustrated supporters that they are doing everything possible to contest Trump’s agenda.

“These are not normal times in our nation,” Booker said as he launched into his speech. “And they should not be treated as such in the United States Senate. The threats to the American people and American democracy are grave and urgent, and we all must do more to stand against them.”

Pacing, then at times leaning on his podium, Booker railed for hours against cuts to Social Security offices led by Trump adviser Elon Musk’s Department of Government Efficiency. He listed the impacts of Trump’s early orders and spoke to concerns that broader cuts to the social safety net could be coming, though Republican lawmakers say the program won’t be touched.

Booker also read what he said were letters from constituents, donning and doffing his reading glasses. One writer was alarmed by the Republican president’s talk of annexing Greenland and Canada and a “looming constitutional crisis.”

“I hear you. I see you, and I’m standing here in part because of letters like yours,” Booker said.

As his speech rolled through Tuesday morning, Booker got some help from Democratic colleagues, who gave him a break from speaking to ask him a question and praised his performance. Booker yielded for questions but made sure to say he would not give up the floor.

“Your strength, your fortitude, your clarity has just been nothing short of amazing and all of America is paying attention to what you’re saying,” Senate Democratic Leader Chuck Schumer said as he asked Booker a question on the Senate floor. “All of America needs to know there’s so many problems, the disastrous actions of this administration.’

According to the Senate’s website, the record for the longest individual speech belongs to Strom Thurmond of South Carolina, who filibustered for 24 hours and 18 minutes against the Civil Rights Act of 1957. As it reached 16 hours, Booker’s speech was the seventh longest in Senate history.

Only one other sitting senators has spoken for longer. In 2013, Sen. Ted Cruz, a Republican of Texas, held the floor for 21 hours and 19 minutes to contest the Affordable Care Act.

Booker invoked Thurmond and the civil rights leader Rep. John Lewis of Georgia on Tuesday morning, arguing that changing history would require the public to get involved.

“You think we got civil rights one day because Strom Thurmond — after filibustering for 24 hours — you think we got civil rights because he came to the floor one day and said, ‘I’ve seen the light,’” Booker said. ”No, we got civil rights because people marched for it, sweat for it and John Lewis bled for it.”

Booker’s speech was not a filibuster, which is a speech meant to halt the advance of a specific piece of legislation. Instead, Booker’s performance was a broader critique of Trump’s agenda, meant to hold up the Senate’s business and draw attention to what Democrats are doing to contest the president. Without a majority in either congressional chamber, Democrats have been almost completely locked out of legislative power but are turning to procedural maneuvers to try to thwart Republicans.

Booker, 55, is serving his second term in the Senate. He was an unsuccessful presidential candidate in 2020, when he launched his campaign from the steps of his home in Newark. He dropped out after struggling to gain a foothold in a packed field, falling short of a threshold to meet in a January 2020 debate.

As Democrats search for a next generation of leadership, frustrated with the old-timers at the top, Booker’s speech could cement his status as a leading figure in the party’s opposition to Trump.

Before taking to the national political stage, Booker was considered a rising star in the Democratic Party, serving as mayor of Newark, New Jersey’s largest city, from 2006 to 2013. A Rhodes scholar and graduate of Stanford University and Yale Law, he started his career as an attorney for nonprofits.

He was first elected to the U.S. Senate in 2013 during a special election held after the death of incumbent Democrat Frank Lautenberg. He won his first full term in 2014 and reelection in 2020.