Normally I’d agree, but this ain’t your average election. A Dem candidate younger than Biden could be out there pounding the campaign trail day after day, generating enthusiasm in a way that Biden now seems physically incapable of doing.
Plus, a large number of voters hate both candidates. A shiny new candidate would be exciting and unprecedented, and would get boatloads of attention. They could easily close the gap with Trump, despite what the polls say.
She’s 70. She can easily make it 5 more years.