Socialist Sen. Bernie Sanders (I-Vt.) has endorsed President Biden’s re-election, closing the door on mounting a third consecutive insurgent White House bid in 2024.

The 81-year-old Sanders, who challenged Biden, 80, for the 2020 Democratic presidential nomination, told the Associated Press he would “do everything I can to see the president is re-elected.”

“The last thing this country needs is a Donald Trump or some other right-wing demagogue who is going to try to undermine American democracy or take away a woman’s right to choose, or not address the crisis of gun violence, or racism, sexism or homophobia,” said Sanders, who famously ran a closer-than-expected primary race against Hillary Clinton in 2016.

“So, I’m in to do what I can to make sure that the president is re-elected.”

Biden, the oldest-ever president, officially launched his re-election campaign Tuesday, saying he and Vice President Kamala Harris were ready to “finish the job.”

“Every generation has a moment where they have had to stand up for democracy. To stand up for their fundamental freedoms. I believe this is ours,” Biden, who will be 82 years old on Election Day 2024, said in a video announcement that recycled his 2020 pledge to win the “battle for the soul of America” against “MAGA extremists.”

Most Democrats do not want Biden to run again in 2024, with 62% favoring someone else to be the party leader and only 37% saying they will support the president for a second term, according to an AP-NORC poll from February.

Asked whether the president should be concerned about a potential primary challenge from another Democrat, Sanders replied: “People will do what they want to do.”

“I think Joe Biden will be the Democratic nominee,” he added. “And my job, and I think the progressive movement’s job, is to make certain that he stands up and fights for the working class of this country and does not take anything for granted.”

So far, Biden is facing two challengers for the Democratic nomination: self-help guru Marianne Williamson and environmental lawyer and anti-vaccine advocate Robert F. Kennedy Jr.

“Running for president was a wonderful privilege,” Sanders said. “I enjoyed it very much and I hope we had some impact on the nature of American politics. But right now, my job is to do what I can as chairman of the [Senate Health, Education, Labor and Pensions] Committee, to see Biden gets re-elected and to see what I can do to help transform policy in America to help protect the needs of workers.”

Former President Donald Trump, Biden’s 2020 opponent, is the current frontrunner for the Republican nomination — though a recent polling analysis shows that if Florida Gov. Ron DeSantis becomes the GOP candidate, he would prevail over Biden.