Election 2024 updates: Beshear says Vance 'ain't from Appalachia' at Harris event

California Gov. Gavin Newsom -- one of Biden's top surrogates and is often floated as a potential replacement at the top of the ticket -- thanked the president for his leadership.

"President Biden has been an extraordinary, history-making president — a leader who has fought hard for working people and delivered astonishing results for all Americans. He will go down in history as one of the most impactful and selfless presidents. Thank you, @JoeBiden," Newsom said in a post on X Sunday.

First lady Jill Biden responded to her husband, President Joe Biden's decision to leave the presidential race on Sunday, reposting his announcement with a heart emoji.

Biden’s granddaughter, Naomi Biden, wrote in a post on X that she is "proud today of my Pop."

"I’m nothing but proud today of my Pop, our President, Joe Biden, who has served our country with every bit of his soul and with unmatched distinction," she wrote. "Not only has he been — and will continue to be — the most effective president of our lifetime, but he has likely already cemented himself as the most effective and impactful public servant in our nation’s history."

"He has been at the center of, and had a material impact on, literally every single major issue that our country and world has faced for 50 years," she added. "Our world is better today in so many ways thanks to him. To the Americans who have always had his back, keep the faith. He will always have ours."

Following Biden’s announcement he would drop out of the 2024 presidential race, Trump railed against him in a post on TruthSocial.

"Crooked Joe Biden was not fit to run for President, and is certainly not fit to serve - And never was! He only attained the position of President by lies, Fake News, and not leaving his Basement," Trump wrote.

"All those around him, including his Doctor and the Media, knew that he wasn’t capable of being President, and he wasn’t," he wrote. "And now, look what he’s done to our Country, with millions of people coming across our Border, totally unchecked and unvetted, many from prisons, mental institutions, and record numbers of terrorists. We will suffer greatly because of his presidency, but we will remedy the damage he has done very quickly. MAKE AMERICA GREAT AGAIN!"

Minutes after President Joe Biden announced he was stepping down from the 2024 presidential race, former North Dakota Sen. Heidi Heitkamp said that while she considers Biden an ally and a friend, Sunday is "a good day for the Democratic Party."

Heitkamp called his decision "a sacrifice he is making for the country."

"He has served this country so ably, it can't have been easy," Heitkamp said, in an interview on ABC News Live.