Republicans led by their vice presidential nominee Senator J D Vance have asked President Joe Biden to resign from his post after he decided not to seek re-election in November, saying his move to withdraw from the race is a clear admission that he is not "mentally fit enough" to serve as the commander-in-chief.

Biden, 81, announced on Sunday that he decided to give up running for re-election as president of the United States and endorsed his deputy Kamala Harris to be the presidential nominee of the Democratic Party— with just 107 days left until the November 5 elections.

“If Joe Biden ends his reelection campaign, how can he justify remaining President? Not running for reelection would be a clear admission that President Trump was right all along about Biden not being mentally fit enough to serve as commander-in-chief. There is no middle ground,” Vance said.

Last week, the 39-year-old Ohio Senator was picked as a running mate by Republican presidential nominee Donald Trump.

“Joe Biden has been the worst President in my lifetime and Kamala Harris has been right there with him every step of the way," he said.

Over the last four years, she co-signed Biden's open border and green scam policies that drove up the cost of housing and groceries, Vance alleged.

"She owns all of these failures, and she lied for nearly four years about Biden's mental capacity--saddling the nation with a president who can't do the job,” he said.

“President Trump and I are ready to save America, whoever's at the top of the Democrat ticket. Bring it on,” Vance said as he was joined by several others from the Republican Party.

House Speaker Mike Johnson said if 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," Johnson said.

House Majority Whip Tom Emmer said If the Democrat party has deemed Biden unfit to run for re-election, he's certainly unfit to control America's nuclear codes.

"Biden must step down from office immediately," Emmer said.

Arkansas Governor Sarah Huckabee Sanders also demanded Biden's resignation.

“Not fit to run for president, not fit to serve as president. Biden should resign immediately,” Sanders said.

Senator Rick Scott said if Joe Biden cannot run for re-election, he is not capable of serving as president for the next six months and needs to resign today.

“While we welcome the news that one of America's most destructive presidents will be denied a second term, it changes very little as to the stakes of this election. We cannot allow the American dream to be destroyed and replaced with California socialism. Come November, we will defeat the Democrats, elect Donald J Trump, take back the Senate and the House, and save our country,” he said.

“Then resign your office. If you can’t run a mere political campaign, you can’t be President,” Senator from Missouri James Hawley said.

Senator Marsha Blackburn from Tennessee said finally, Biden has realised what the rest of the American people and even his own party already knew that he is not only the wrong leader for America but is wholly incapable of doing the job of President of the United States.

"But he didn’t go far enough. If Joe is too weak to stay in the race for the presidency, he should resign as our commander-in-chief immediately,” Blackburn said.

Congressman Harriet Hageman from Wyoming said it has long been apparent that Biden has no business running a popsicle stand, let alone the most powerful nation on Earth.

“His decision to withdraw from the race is the right one, but it is not the only such decision he should make: He should now resign from the presidency itself,” she said.

“If you are unfit to stand trial. If you are unfit to run for re-election. Then you are unfit to be president of the United States. Biden must resign,” Congressman Tom Tiffany said.

Congressman Carlos A Gimenez said: "If Joe Biden isn't capable enough to seek re-election, he's not capable enough to remain serving as our President." "President Biden does not have the capacity to be the President of the United States. Our enemies are seeing this, and it puts America at risk. America is less safe than ever before because Biden has proven to be a weak leader. For the good of the country, Joe Biden should step down and resign," Gimenez said.

Congressman Josh Brecheen said if Biden is not well enough to be the next Democratic nominee, he is not well enough to continue serving as President.

“President Biden should resign immediately,” he said.

Whoever is the Democratic nominee is going to have a tough time defending the Biden-Harris record, which has been marked by historic inflation, crime, and wide-open borders. The American people have seen enough, Brecheen said.

“President Joe Biden's announcement that he will suspend his reelection campaign is an admission of something that Americans have observed for a long time – he is not fit to be president, which also means he can no longer serve as commander-in-chief,” said Congressman Ron Estes.

“Vice President Kamala Harris, numerous congressional Democrats, and the media have shamefully ignored and willfully misled the American people by hiding the true cognitive state of President Biden – their deception is a disgraceful disregard for the American people. For the good of the country and for our national security, President Biden should resign immediately,” he demanded.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.