Besieged by rising doubts of his fitness and electoral hopes, President Biden has been dealt a body blow by one of the most widely respected pollsters - among those who still believe in pollsters.

In a post on Substack, left-wing polling wizard Nate Silver urged Biden to "stand down" if he is not able to reassure the public he can run a "normal campaign."

Silver cited Biden's invisibility as a red flag - urging his team to "put up or shut up."

Biden urged to STAND DOWN

A year ago, Silver said, he would have bet on a Biden victory, but changed circumstances have altered his assessment.

"H] e's losing now and there's no plan to fix the problems other than hoping that the polls are wrong or that voters look at the race differently when they have more time to focus on it," Silver wrote.

Silver cited Biden's decision to skip the Super Bowl as an example of his failure to meet expectations.

"This really isn't too much to ask," Silver wrote. "These are the sorts of interviews that every other recent president has done."

The question of Biden's age was reopened by Special Counsel Robert Hur's report, which described Biden as an "elderly man with a poor memory."

Biden's angry, defensive reaction only made things worse. Democrats are now in the uncomfortable position of insisting that Biden is fine - or even vigorous and alert - despite deep and broad public skepticism.

Silver noted that Biden's most fervent supporters "are really arguing that Democrats could win despite Biden and not because of him."

"Disqualifying" age concerns

There are currently no signs that Democratic elites have abandoned Biden, despite persistent speculation of a palace coup.

When Democrats embraced Biden in 2020, he was pitched to voters not on his own merits, but as the Trump alternative.

Then as now, Biden has focused on Trump's alleged moral failings, painting his Republican rival as would-be dictator - but it's not clear that fearmongering will be enough to overcome public disapproval of Biden's job performance, or fear about his cognitive decline.

Despite efforts to equate Biden's frequent mental slips with Trump's gaffes, voters do not see the two as equally concerning.

"Biden is probably a below replacement-level candidate at this point because Americans have a lot of extremely rational concerns about the prospect of a Commander-in-Chief would be 86 years old by the end of his second term," Silver wrote.

"It is entirely reasonable to see this as disqualifying," he concluded.