Biden under pressure: could retire at weekend. Nbc reports a staff source: 'Close to the end'

Meanwhile, an overwhelming majority of Democrats approve of Vice President Kamala Harris replacing Joe Biden in the White House race, should the president decide to step aside. This was revealed in the Economist/YouGov poll released on Thursday: 79% of Democrats would support Harris as the party's nominee. The news comes as a growing number of Democrats are calling for the president to step aside in the wake of the poor performance in the debate against former president Trump last month.

Biden was supposed to attend a conference in Las Vegas on Wednesday afternoon, but cancelled at the last minute after testing positive for the coronavirus. The White House said he had mild symptoms and would return to his home in Rehoboth Beach to isolate himself.

A few hours before the White House announcement, Biden had said in an interview that he would consider stepping down if doctors told him he had a 'medical condition', passing the baton to Harris. "If any medical condition came up, if the doctors told me 'you have this problem and that problem'..." he said.

To date, Biden has given shifting reasons as to what might make him decide to step aside. In an interview with ABC News on 5 July, after his poor performance in the debate with Trump, he said that only the 'Lord Almighty' could convince him. A week ago, he said during a press conference that he would stay in the race unless his aides told him he had no chance of winning a second term.

The Covid news not only interrupted two days of campaigning in Nevada, but also aggravated Democrats' anxieties about his re-election campaign, which has been teetering for nearly three weeks after a poor performance in the first debate with Trump. Democrats and voters alike are deeply concerned about Biden's age, health, and stamina. In recent weeks, the president has maintained a busy campaign schedule to demonstrate vigour in the face of doubts, but the Covid news further weakens his position.

Many Democrats have called on him to step aside as the party's presidential candidate. The political crisis facing the Biden campaign was further aggravated when on Wednesday the call to step aside also came from Congressman Adam Schiff, a prominent House Democrat and a leading favourite in the California Senate race in November.

Schiff is the first elected Democrat to publicly suggest that Biden give way to a new nominee since a gunman attempted to assassinate Trump. While the nation's attention these days was focused on the shooting, and somewhat less on the difficult position Biden finds himself in, privately, Democrats continued to debate Biden's eligibility. Schiff, with his request, brought national attention back to Biden, becoming the 23rd Democrat in Congress to call for his release.

In recent days, Biden has said that Democrats continue to be supportive of him staying in the race, but polls show that between 40 and 65 percent believe the president should drop out.