You're in charge of any campaign you want (post 1980), and you can change one thing. What is it?

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Gore 2000. I'd change two things:

1. Get him to pick Bob Graham (edit: or Jeanne Shaheen) instead of Lieberman

2. Scratch the word 'lockbox' out of his debate prep notes

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Clinton 2016. Make her spend more time in the midwest, pretending not to hate those cheese-eating yokels in Wisconsin, hoagie hicks in Pennsylvania, and Canadians with somehow a more ridiculous accent (Michiganders).

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Sanders 2020:

1. Tone down the specifities on new big spending programs, which made him vulnerable to the idea that he's unrealistic and unelectable. Instead, focus your rhetoric on taking on real and perceived corruption in Washington and Wall St. I think the latter would have helped him with a lot of self-identified moderates and some minorities. (EDIT: also, he always seemed more comfortable with the populist stuff than the wonky stuff)

2. Hire better people. Folks like David Sirota and Nina Turner really seemed to believe that the centrist lane would remain divided long enough that Bernie would emerge as the clear frontrunner, which was risky at best and foolish at worst.

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Yang 2020 (not that he would ever have won, but his influence on the party may have been greater):

Don't make UBI the flagship campaign promise. I get that he needed a shtick to get traction, and I'm not entirely sure what that could have been, but "free money for all" made him seem completely unserious to most voters.

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Dukakis '88: "Bernard, that's a loaded question and you know it."

The cold response is just his personality though, it's really hard to see him give a good response to that. Plus I don't think the Dukakis team expected such a question to be asked.

More broadly though, being more "tough-on-crime" would have helped him and probably saved him from being asked that infamous question. I know that wasn't his ideological conviction on crime, but this was the 1980's baby, tough on crime was in vogue.