I’ve seen numerous users on Twitter talking the past couple of days about Biden dropping out after being diagnosed with a medical problem. No specifics have been provided.
Unless something catastrophic happens regarding Biden's health (stroke, heart attack), at this point the Democrats need to stick with him and try to drag him across the finish line. If Biden suddenly stepped down now, all out war would erupt within the party. Bernie's supporters would argue that he should get the nomination, since he won more primaries than anyone but Biden, and has the second highest delegate count. Kamala Harris' supporters will claim that, as the VP candidate, she should be elevated to the top spot on the ticket. Hillary, seeing one last chance at the presidency, may go for broke and jump into the fray.