On Tuesday, Lloyd Doggett became the first Democratic US lawmaker to publicly urge Joe Biden to withdraw from the race for the White House, citing the president's lackluster performance in last week's presidential debate.

"Recognizing that, unlike Trump, President Biden's first commitment has always been to our country, not himself, I am hopeful that he will make the painful and difficult decision to withdraw. I respectfully call on him to do so," the Texas Congressman said in a statement.

On June 28, US House Speaker Mike Johnson suggested that the presidential cabinet should consider removing Biden from office by exercising the 25th Amendment, in light of the fallout witnessed after the presidential debate. 

Read more: Major Democratic donors wondering what to do about Biden: NYT

A recent Morning Consult survey published last week revealed that 60% of US voters believe Biden should "definitely" or "probably" be replaced as the Democratic candidate.

The poll's findings, which included 2,068 respondents, come as rumors and calls circulate regarding the replacement of Biden as the Democratic candidate.

Biden's performance has left some Democrats questioning his viability as the party's nominee, CNN reported, citing Democratic sources.

One source mentioned that it is hard to see how Biden can become the party's nominee, while another characterized him as "incoherent", according to the report on Thursday.

21% of Democratic voters believe Biden should "definitely not" be replaced, while 20% say "probably not."

When asked to choose between Biden and Trump, 45% chose Biden and 44% chose Trump. 

Read more: 'I don't debate as I used to, but I know how to tell the truth': Biden

On another note, Trump was recently granted immunity from prosecution on election subversion allegations relating to official conduct as president.

But he may still face prosecution for unofficial actions, as per a ruling by the US Supreme Court on Monday.

The court cited in its ruling that constitutional separation of powers means "the nature of Presidential power entitles a former president to absolute immunity from criminal prosecution for actions within his conclusive and preclusive constitutional authority. And he is entitled to at least presumptive immunity from prosecution for all his official acts. There is no immunity for unofficial acts."

In response to the Court's ruling, Biden said that the Court was setting a "dangerous precedent," adding that the law was equally imposed on everyone in the US and that there were "no kings in America."