Facing a stunning end to a 50-year-long political career, Biden announced Sunday he will no longer seek another four years in office after his physical and mental acuity were called into question following a primetime debate that broadcast to the world him struggling to finish sentences, giving confused looks and fumbling through his answers.

Biden, 81, wrote in a letter posted to social media, “It has been the greatest honor of my life to serve as your President. And while it has been my intention to seek reelection, I believe it is in the best interest of my party and the country for me to stand down and focus solely on fulfilling my duties as President for the remainder of my term.”

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He said he would address the nation later in the week about his decision. He did not immediately endorse Vice President Harris or any other candidate to be the party’s nominee in November.

He further wrote, “For now let me express my deepest gratitude to all those who have worked so hard to see me reelected. I want to thank Vice President Kamala Harris for being an extraordinary partner in all this work. And let me express my heartfelt appreciation to the American people for the faith and trust you have placed in me.”

He withstood weeks of mounting pressure from his party, vowing to stay in the race so strongly that at one point he suggested only a higher power could convince him otherwise.

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He acknowledged multiple times after the debate that he had a bad night, where his aides said he had a cold. He had just returned from a foreign trip, which was blamed for his sickness despite his being out of the public eye while staying at Camp David for nearly one week before he went head-to-head with Trump.

The president’s campaign had pressed for an early debate date because he thought it might turn into a moment that could change polls, but it did anything but.

On the other hand, former president Trump found a new wind in his sails in scoring major legal and political wins recently, particularly after an attempted assassination that reinforced Republicans behind his campaign right before what turned out to be a jubilant and unified coronation at the Republican National Convention.