Mr. Biden’s campaign has not said how much money he has raised since mid-March, when the virus began taking its toll on the country, but multiple fund-raisers said that giving was slowing and that they were reluctant to make aggressive requests for cash at this fragile moment, as the campaign itself readies for a 100 percent virtual and digital operation.

These should be some of the busiest and headiest days for Mr. Biden and his fund-raising team in normal times, now that he has knocked out all of his rivals but Senator Bernie Sanders, who trails by a nearly insurmountable 300 delegates. But instead he has found himself holed up in Wilmington, Del., and limited so far to three video fund-raisers from a makeshift studio installed in the retrofitted rec room of his house.

“It is definitely harder to raise money now,” said Mathew Littman, a former Biden speechwriter in California who is organizing a video fund-raiser and recently started a separate super PAC to raise money to support Mr. Biden in Western states. “The fun aspect of the fund-raiser is taken out of it.”

“You have to be very sensitive to what’s going on with people’s lives,” Mr. Littman added. “This is definitely a much softer pitch than it was two weeks ago because the economy is going to be in either recession or a depression for a bit.”

Some top fund-raisers said the notion of thumbing through call lists of friends to raise money for politics during an unprecedented economic and health crisis was tone deaf. Others are simply focused elsewhere right now. They are investors who have seen their portfolios hammered, business owners trying to triage their holdings and take care of their employees, philanthropists with links to cultural institutions at risk of collapse, or even health care systems bracing for the virus’s full impact.