From a column on politico.com by Jonathan Martin headlined “Senior Democrats’ Private Take on Biden: He’s Too Old”:

High-level Democrats are rallying to President Biden’s reelection, not because they think it’s in the best interest of the country to have an 82-year-old start a second term but because they fear the potential alternative: the nomination of Kamala Harris and election of Donald Trump.

Not that many of them will say it publicly, at least not that directly.