2020 Democratic Nominee if Hillary Loses

[Mister Mets]

If Warren wants it, she'll be a frontrunner.

Otherwise I'd bet on Gilibrand, Julian Castro or Kamala Harris. Gilibrand is a broadly acceptable Senator with a progressive reputation who would help the party have a second shot at electing the first female President. Kamala Harris has a reputation for leadership on justice issues, and could appeal to large segments of the party. Julian Castro is the party's most prominent young Hispanic.

I could see Bill De Blasio running, but he's probably too urban for the primaries.

Whoever is Clinton's running mate is likely to have an elevated profile. It's typically not a path to the nomination, but the reasons Ferraro, Bentsen, Lieberman, Edwards and Palin didn't win nominations might not apply to the next guy.