Newsom is easy to paint as an out-of-touch elite California limousine liberal. One thing that helps with that portrayal... is that it is pretty much spot on, he is exactly that. Newsom isn't going to win over the blue collar workers who are often union members, that Trump has been gleaning away from the Dems.
On the Democratic side, Andy Beshear (Kentucky governor) and Josh Shapiro (Pennsylvania governor) stand out to me.
On the Republican side, Rubio or Haley I think would have been tolerable Republican presidents who maintained the broad bipartisan foreign policy consensus that Trump has upended. They would have respected the rule of law, elections, and the democratic process, which Trump has undermined trust in among 35-40% of the US population (and now he needs to "secure" these elections against misperceptions he created with his lies).
Had they been nominated in their previous primary bids and won, I may not have voted for them, but I may have stayed home and not voted at all, instead of casting my first vote in a presidential election since 2008 for Harris. Whom I didn't support per se or vote for on the basis of her policies, but rather because of the unique danger Trump poses to democracy, the rule of law, and the US Constitution.