Biden's authority is draining away in real time

• Joe Biden's reelection bid is looking less and less tenable. 
• Top Democrats, including Barack Obama, are said to be encouraging him to give up. 
• Biden's holding on, but each new voice weakens him further.

As former President Donald Trump was delivering his marathon speech at the RNC Thursday night, President Joe Biden was holed up in isolation, having been diagnosed with COVID-19.

Biden is still battling to save his candidacy after the disastrous debate with Trump last month — for weeks, he's insisted that he won't be quitting and is the only Democrat who can beat Trump.

But the pressure to quit from friends and former allies is getting more intense every day.

On Thursday, The Washington Post reported that former President Barack Obama had added his voice to those who doubt Biden's viability as a candidate.

It's a serious blow for Biden, who has long counted on the political support of his former boss, who remains among the most respected figures in the Democratic Party.

It comes after former House Speaker Nancy Pelosi, another friend and former ally, is said to have told Biden that if he doesn't stand aside, Democrats could lose control of the House in November and funding could dry up.

Senate Majority Leader Chuck Schumer, per reports, told Biden on a call Saturday that it'd be best if he dropped out, too.

So that means the most powerful Democrat in Congress, its most beloved former president, and its most influential House speaker are all telling Biden to think again.

The support of his party that sustains his position leading the country is draining away — with some congressional Democrats now prepared to make their calls in public.

It's a painful moment for Democrats, with Biden having seemed like a far more viable candidate just weeks ago.

He was polling neck-and-neck with Trump, who had just suffered a huge blow to his political fortunes after being found guilty on felony charges in his New York hush-money trial.

But the June 27 debate, in which Biden repeatedly lost his train of thought and appeared confused, upended the campaign.

It reignited concerns that Biden, at 81, is too old to serve another term.

The failed assassination attempt on Trump at a Pennsylvania rally last Saturday has also galvanized Republican support for the former president.

Trump's vigorous response to the attack also provided a stark contrast to Biden, even though Trump is only a few years younger.

Many seem open to a different Democratic candidate.

An AP-NORC Center for Public Affairs Research poll found that 6 out of 10 Democrats believe that Vice President Kamala Harris, who's considered mostly likely to replace Biden on the Democratic ticket, would make a good president.

Biden has so far shot down the calls to step aside, with the campaign dismissing reports that Obama's support is waning as "baseless," and insisting that Biden would remain the candidate.

An advisor told media outlets: "Joe Biden is his party's nominee. He's the president of the United States. He's running for reelection."

But The New York Times on Thursday reported what could be a shift.

It said, citing people close to him, that Biden was beginning to acknowledge that he may not be able to win in November.

Some aides, though, were still arguing that he can stay in the race and win, per The Times.

NBC News reported that he feels angry and betrayed by Democrats turning against him.

As the weekend approaches, it appears likely that Joe Biden's attempts to rescue his reelection bid have reached a crunch point.