You'd think that to at least have a fighting chance, the Democrats would have picked a credible candidate.
They've had four years.
I’d suggest that the Democrats have more than a ‘fighting chance’ as it is. They’ve actually got a fighting chance of doing the treble (White House, Senate and House).
Polls* have Biden on around 52% and Trump on around 43.5%**. Well outside a 3% margin of error.
But to follow on with your point, what would that lead be if the Democrats had found a better candidate?
* 538 on 30 Oct.