Democratic politicians hailed US President Joe Biden’s historic decision on Sunday not to seek re-election, praising him for putting his country and his party before himself.

Republicans called on him to resign from office, saying that if he could not run for another term, office, then he is unable to serve as president.

Mr Biden’s announcement came after more than two weeks of Democrats urging him to withdraw from the race.

Nearly three dozen lawmakers had publicly called on him to end his re-election bid. Others had voiced concerns privately about what the ramifications would be for down-ballot Democrats if he remained in the race. When the president heeded those concerns, Democrats called it a selfless move.

“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,” Senate Majority Leader Chuck Schumer said in a statement.

Republicans have seized on Mr Biden’s poor debate performance last month to batter him as incapable of serving four more years. Now that he is out of the presidential election, many said he should resign his office, too.

“If Joe Biden is not fit to run for president, he is not fit to serve as president. He must resign the office immediately. November 5 cannot arrive soon enough,” House Speaker Mike Johnson said in a statement.

“If the Democratic party has deemed Joe Biden unfit to run for re-election, he’s certainly unfit to control our nuclear codes. Biden must step down from office immediately,” tweeted Minnesota Republican Representative Tom Emmer.

Donald Trump’s running mate, JD Vance, who was initially expected to face off against Kamala Harris in a debate, linked her on Sunday to all Mr Biden’s policies.

Mr Vance said Ms Harris “co-signed” Mr Biden’s border and climate policies and that those drove up prices for housing and groceries.

“She owns all of these failures,” Mr Vance said on X, formerly Twitter.

“President Trump and I are ready to save America, whoever’s at the top of the Democrat ticket,” the Ohio senator said. “Bring it on.”

Mr Biden’s former chief of staff, Ron Klain, called on Democrats to quickly unite around Vice President Kamala Harris as the natural successor to Mr Biden, saying on social media that “it’s time to end the political fantasy games and unite behind the only veteran of a national campaign”.

“Let’s get real and win in November,” Mr Klain said.

But in their initial statements, many Democrats made no mention of Ms Harris. Some are calling for an open process in selecting the next Democratic presidential nominee.

Mr Schumer and Senator Dick Durbin, the top two Senate Democrats, did not offer support for Ms Harris.

“Now the Democratic Party must unite behind a candidate who can defeat Donald Trump and keep America moving in the right direction. I will do everything in my power to help that effort,” Mr Durbin said.

Rep Lloyd Doggett of Texas, the first House Democrat to call on Mr Biden to step down, said “once again President Biden comes through for America, putting country over ego in a way that Donald Trump never could”.

He said that while Ms Harris is clearly the leading candidate to replace Mr Biden, “we should be open to all talented individuals who wish to be considered”.

Many Democrats did quickly assemble behind Ms Harris.

The leaders of two of the largest Democratic House caucuses, Representatives Pramila Jayapal, chair of the left-wing Congressional Progressive Caucus and Annie Kuster, chair of the moderate New Democrat Coalition, endorsed Ms Harris on Sunday afternoon.

The endorsements were part of an effort among Democrats in Congress to quickly assemble behind a candidate and try to put behind them the weeks of intraparty tension that have marked the aftermath of the June 27 debate.

“Millions of Americans cast their ballots for Joe Biden and Kamala Harris in the primary. Vice President Harris has proven time and time again that she can prosecute the case against Donald Trump and campaign vigorously for Democrats down the ballot,” Ms Jayapal said in a statement.

The Congressional Black Caucus also, through its political action committee, gave its support to Ms Harris as the next Democratic nominee. The black caucus had stood by Mr Biden since the debate last month even as many other Democrats called for him to step aside.

Several Democratic senators individually weighed in with support for Ms Harris, including Patty Murray of Washington, Mark Warner of Virginia, Chris Murphy of Connecticut and Mazie Hirono of Hawaii.

The reaction to Mr Biden’s announcement reverberated around the county and the world.

Former President Barack Obama saluted his vice president of eight years.

“Joe Biden has been one of America’s most consequential presidents, as well as a dear friend and partner to me. Today, we’ve also been reminded — again — that he’s a patriot of the highest order,” Mr Obama said.

Internationally, Israel’s president, Isaac Herzog, offered “heartfelt thanks” to Mr Biden for supporting the Israeli people over his long career.

Mr Herzog wrote on social media that Mr Biden was the first American president to visit Israel at a time of war, after the October 7 Hamas attack and called Mr Biden a “symbol of the unbreakable bond between our two peoples”.

Australian Prime Minister Anthony Albanese thanked Mr Biden for his leadership and said the alliance between their two countries “has never been stronger”.

Polish Prime Minister Donald Tusk acknowledged the difficult decision Mr Biden had to make and said: “Poland, America and the world are safer and democracy stronger” because of the US president.