FILE PHOTO: U.S. President Joe Biden gestures as he speaks at a press conference during NATO's 75th anniversary summit, in Washington, U.S., July 11, 2024. / REUTERS/Yves Herman

U.S. President Joe Biden on July 21 ended his reelection campaign. He said in a letter posted on X that he would remain in office until the end of his term and address the country later this week on his decision.

Below are reactions from politicians, industry and advocacy groups, and other observers:

FORMER PRESIDENT DONALD TRUMP

In a phone call with CNN minutes after Biden announced his exit from the 2024 race, former President Trump responded, “He is the worst president in the history of our country. He goes down as the single worst president by far in the history of our country.” Trump also said he thought Vice President Kamala Harris will be easier to defeat than Biden would have been, according to CNN.

CHUCK SCHUMER, SENATE MAJORITY LEADER

"Joe Biden has not only been a great president and a great legislative leader but he is a truly amazing human being. His decision of course was not easy, but he once again put his country, his party, and our future first. Joe, today shows you are a true patriot and great American," the Democrat said in a statement.

ELISE STEFANIK, HOUSE REPUBLICAN CONFERENCE CHAIRWOMAN

"If Joe Biden can’t run for re-election, he is unable and unfit to serve as President of the United States. He must immediately resign," Stefanik said in a statement.

GAVIN NEWSOM, GOVERNOR OF CALIFORNIA

"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," Newsom posted on X.

DONALD TRUMP JR

"Kamala Harris owns the entire left-wing policy record of Joe Biden. The only difference is that she is even more liberal and less competent than Joe, which is really saying something. She was put in charge of the border and we saw the worst invasion of illegals in our history!!!" Donald Jr said on X.

ERICH PICA, PRESIDENT OF FRIENDS OF THE EARTH ACTION

"We thank President Biden for his decades of leadership and support the decision to end his re-election campaign. While far from perfect, Biden has taken some historic steps to address the climate crisis by passing the Inflation Reduction Act and kickstarting major investments in renewable energy.

"What’s at stake in this election remains the same: Trump is an existential threat to our democracy and the planet and would guarantee a full descent into climate chaos," Pica said in a statement.

GRETCHEN WHITMER, GOVERNOR OF MICHIGAN

"President Biden is a great public servant who knows better than anyone what it takes to defeat Donald Trump. His remarkable work to lower prescription drug costs, fix the damn roads, bring supply chains home, address climate change, and ensure America’s global leadership over decades will go down in history. My job in this election will remain the same: doing everything I can to elect Democrats and stop Donald Trump, a convicted felon whose agenda of raising families' costs, banning abortion nationwide, and abusing the power of the White House to settle his own scores is completely wrong for Michigan," Whitmer said on X.

DICK DURBIN, SENATOR AND MAJORITY WHIP

"Throughout his public career, Joe Biden always put country first. His four years as President made it clear that he was determined to put our country back on track and restore the soul of our nation. America will be forever grateful for all he has given to this country," Durbin posted on X.

ALLAN LICHTMAN, AMERICAN UNIVERSITY HISTORY PROFESSOR

"The Democrats could still salvage the contest key if they unite behind Harris!" Lichtman posted on X.

JAY TIMMONS, NATIONAL ASSOCIATION OF MANUFACTURERS PRESIDENT AND CEO

"We have seen significant manufacturing job growth in recent years, and there are now more manufacturing jobs in America than at any point since 2008. We will continue working with President Biden until he passes the torch to the next commander in chief," Timmons said in a statement.

STEVE SCALISE, HOUSE MAJORITY LEADER

"Democrat party bosses just proved that they have absolutely no respect for their own voters. After lecturing others about democracy, they just forced Joe Biden off the ticket—trashing the primary choice of 14 million of their own voters," Scalise, a Republican, said on X.

NAOMI BIDEN, JOE BIDEN'S GRANDDAUGHTER

"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. 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," Biden posted on X.

VOTERS OF TOMORROW

The Gen Z-led organization that says it engages young Americans in politics and government, praised Biden "for delivering the most pro-youth agenda in American history."

"We are ready to mobilize young people to elect Kamala Harris as president," the group said.