Terry McAuliffe?

[Skill and Chance]

Republicans wouldn’t have a hard time "demoniz[ing]" him. He’s a shady, unlikable insider/career politician and partisan hack who only won his races (including 2021) because he was running in an inflexible blue state. He’d lose to any halfway competent Republican opponent in a national race.

Yes, he has all of the same problems as Hillary Clinton with none of the history-making potential to drive up Dem turnout.  McAuliffe would be a very bad choice for a presidential nominee and would alienate the median voter in the EC.  

He's not a bad fit for VA, though.  The median VA voter tends to value career politicians with policy chops.  They also aren't fazed by angling for questionable government contracts, because that's probably part of their day job.

[Skill and Chance]

He'd have to get elected in November.  That's far from a given, even if he is the current favorite.

McAuliffe only got 47.5 percent of the vote when he ran against Ken Cuccinelli.  Cuccinelli likely would have won were it not for a pro-choice Libertarian who siphoned votes away from Cuccinelli, who has made opposing abortion his signature issue.  Now Virginia has changed since 2013 and 2013 was a Repubican year, but this year is likely to be a Republican year to some degree in Virginia. 

When you win with 47.5% of the vote it begs the question of how popular you are.  McAuliffe is favored, and I'd say, gun to my head, that he'd be the winner, but I don't see where he's PERSONALLY popular.  He's the candidate because the replacements for Northam all had their baggage, as did Northam.  He's the "safe" pick.  The question is (A) how Democratic is Virginia right now and (B) how much actual personal popularity does Terry McAuliffe have with Virginia voters.  My prediction is that he'll win, but he'll be shocked by how close it is.

Other way around, T-Mac would've reached 50 without that third party.

And given that he's unlikely to have someone as incompetent as Robby Mook, it seems unlikely for a stumble.

I don't know about your analysis regarding the Libertarian candidate in that race, but "Robby Mook" says it all.

Robby Mook ran his campaigns to win an election for class president of a Northeast private college.  Totally incompetent at reaching the median voter!