People close to President Biden are "furious" that a pressure campaign calling for him to step aside is picking up speed, according to reports. 

Biden is self-isolating in Rehoboth, Delaware, after testing positive for COVID-19. 

"Lots of anger toward some donors for talking of $ drying up if he doesn’t quit, toward what they see as muted support from Pres. Obama, and toward Dem leaders who one source says are ‘hiding’ behind statements," CBS News reporter Robert Costa posted on X. "If they want him out, they’ll have to push, source adds."

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Costa added that Biden feels "disrespected" but that no one has figured out "an effective way to quiet this drift of nervous Democrats away from Biden and know many Dems want Biden to just break at some point soon."

Multiple Democrats have come out in recent weeks to call for Biden to exit the race amid questions about his health. 

Sources told Fox News that Biden's COVID-19 diagnosis has forced him to slow down for a period of reflection. 

Democratic House and Senate members sense there's a shift in Biden’s thinking that he will remain at the top of the ticket, the source said.