Most electable democrat

[Absentee Voting Ghost of Ruin]

Biden, if he runs a good campaign. Biden is pretty much the only current candidate who has a realistic shot at getting all plausible anti-Trump voters to turn out and vote for him in large numbers.

Personally, I prefer Warren and like Sanders, but either of them would be operating with a bit of a handicap that is unlikely to be mitigated by even a superb campaign. (For Warren, it's sexists who won't vote for a woman, ever. For Bernie it's people who won't vote for a socialist, ever.) Being gay will hurt Buttigieg about the same amount, but his lack of experience will hurt his numbers at least that hard again. I think all plausible Democratic nominees can win. (Mr. Trump is the worst candidate in living memory, sinking even below his own 2016 campaign.) But Biden has the potential for the largest margin of victory, so if he runs well (which is by no means guaranteed) Biden will win in circumstances where his rivals would lose, even with note-perfect campaigns.

As to whether or not that makes him the best nominee... well, I fear the chances of him running a below-average campaign or otherwise blowing the race are pretty high, much higher than the other candidates. Also, if Mr. Trump is not the Republican nominee (and I don't think he will be), then the whole field changes and this all goes out the window.

[Absentee Voting Ghost of Ruin]

... Also, if Mr. Trump is not the Republican nominee (and I don't think he will be) ...

Runeghost,
Can you expand on this please.
How is it possible that you believe that trump will not be the Rep 2020 nominee?
In what scenario is this possible?

See the thread on the increasingly steeper slope of his mental decline. Go watch him slur and twitch his way through a speech at his rally tonight.  While it's possible that the Republicans will nominate him and cart him around on campaign like a popular but failing animatronic prop, I think that the odds his physical and mental deterioration will keep him off the ballot one way or another are very likely (say, over 75%).

Maybe I'm still being too generous to Republicans with when they'll replace him, and maybe I'm flat-out wrong about how poor his condition is and how rapidly his decline is accelerating. But that's what it looks like to me. (Plus Trump resigning or declining to run for reasons of ill-health stands a good chance at letting him personally escape prison, and lets the Republicans both have their cake and eat it too.)