Stewart is an interesting choice. He knows more about how the federal government works than most of the field and has demonstrated the needed gravitas when before Congress. And he will only be 65 at the end of two terms. OTOH, he has no significant Chicago connection and his line cannot be directly linked to any Biblical wizards, but these are suggestions, not requirements. 
Oh, and his college was referenced in one of the best Steely Dan songs, My Old School.
So, Jon Stewart is in. Next?
Franken’s well is poisoned. 
Oprah is the idiot who gave us Dr Phil and other quacks. After viewing the re-release of The Exorcist she was visibly shaken saying, “It was so real!” We already had a president afraid of broccoli. We don’t need one frightened by pea soup.
Oops!
A recent poll of 5400+ registered voters (I’ll track down the link if someone insists, but I think I found the link here) asked “If the election were held today and the only choices were Donald Trump and XXX who would you vote for?”
There were seven different XXX’s: the five front-runners and two dark-horse women.
Biden and Sanders tied for 2nd place in that survey, getting 50% each (with 8-9% undecided). Warren (46%) and Harris (45%) were in 4th and 5th place.
Who was in 1st place? Michelle Obama with 51% (but only 7% undecided).
I assume Barack would want to help. He’d probably qualify for security clearance, not that that matters anymore. I’ve given up political prognostication, but Obama might be the very best choice!
Joe Kennedy III
LeBron James. OK, maybe not in 2020 (though he’ll be 35 in December), but don’t be shocked if he pursues politics after basketball.
I’d say Noam Chomsky, but I’m guessing you guys would say he’s too old.
If it improves the chances of getting Trump out, I’d say run Mitt Romeny or Jeb Bush.
Honestly, I’d have to say “me”.
It’s ludicrous, for example, that there are no Democrats looking to impeach Trump for running a sham charity for veterans. If even the Democratic Dark Horses are so far out of touch with the right that they don’t understand how integral “support the troops” is to the other side, then all of them are at risk of losing to Trump out of sheer separation from reality.
I was reading the Wikipedia page on Gulliver’s travels, yesterday, and reminded of the Laputans. Y’all need to invest in flappers.