WASHINGTON — President Joe Biden has withdrawn from the 2024 presidential race, he said in a letter posted to social media on Sunday, creating an unprecedented vacancy at the top of the Democratic ticket a month before he is set to formally accept his party’s nomination.

He will remain in office until the end of his term.

Biden’s withdrawal followed a weeks-long pressure campaign from party insiders after his disastrous June 27 debate performance against Republican nominee and former President Donald Trump.

The move throws more chaos into an already unusual presidential race, and it was not immediately clear on Sunday how Democrats would choose a replacement for Biden in the November election. Vice President Kamala Harris, however, could be in contention for the top spot.

Biden did not endorse a replacement in that statement, but did praise Harris as “an extraordinary partner” in the administration’s accomplishments.

In a follow-up message less than 30 minutes later, Biden endorsed Vice President Kamala Harris to put his palace first on the Democratic ticket.

Biden did not give specific reasons for his resignation, but said he believed it was in the best interest of the country.

“While it was my intention to seek re-election, I believe it is in the best interests of my party and the country that I step down and focus solely on fulfilling the duties of my president for the remainder of my term,” Biden wrote in the one-page letter.

Biden, 81, appeared weak and confused at several points during the debate, leading to concerns among elected Democrats and the party’s voters that he would no longer be able to govern or challenge Trump’s bid to reclaim the White House.