Rank speculation? Yes. Pressing issue of our time? No. And I'm sure I'll hear all that and a lot more in the comments. But the GOP gets to play primaries and I'm jealous.
But who's running for the Dem nomination in 2016? The full list and method is below, but here's whom I come up with as possibilities not even "likelies:"
Al Gore
Chris Coons (DE-Sen)
Kirsten Gillibrand (NY-Sen)
Bob Casey (PA-Sen)
Mark Warner (VA-Sen)
John Hickenlooper (CO-Gov)
Dan Malloy (CT-Gov)
Martin O'Malley (MD-Gov)
Jay Nixon (MO-Gov)
John Lynch (NH-Gov)
Andrew Cuomo (NY-Gov)
Hillary Clinton
Kathleen Sibelius
Tom Vilsack
David Petraeus
Two good ones from the comments:
Rahm Emanuel (Mayor-Chicago)
Gavin Newsom (LtG-CA)
Promoted from the screen below by comments:
Brian Schweitzer (Gov-MT)
In the last century+ all presidents have been either, including last example: vice presidents (Bush 41), governors (Bush 43), senators (Obama), cabinet secretaries (Hoover), generals (Eisenhower), or a representative (Garfield). Representatives who weren't senators later are rare. As far as I know, the only ones are Madison, Garfield, and Polk, and Polk was a governor. Garfield is the only one that didn't also have some executive branch experience... and that didn't work out very well for him, did it?
So, given that here's a preliminary screen (age in 2016 in parentheses). The list at the top excludes very old candidates, ones with apparently insurmountable political issues, or come from somewhere that makes them problematic. The latter two are just guesses. I'd appreciate your feedback.
Vice Presidents:
Gore (68)
Biden (74)
Mondale (88)
Senators:
Begich (54)
Pryor (55)
Feinstein (83)
Boxer (76)
Udall-CO (66)
Bennet (52)
Blumenthal (70)
Carper (69)
Coons (53)
Nelson (74)
Inouye (92)
Akaka (92)
Durbin (72)
Harkin (77)
Landrieu (61)
Mikulski (80)
Cardin (73)
Kerry (73)
Levin (82)
Stabenow (66)
Klobuchar (56)
Franken (65)
McCaskill (63)
Tester (60)
Nelson (75)
Reid (77)
Shaheen (69)
Lautenberg (92)
Menendez (62)
Bingaman (73)
Udall (68)
Schumer (66)
Gillibrand (50)
Hagan (63)
Conrad (68)
Brown (64)
Wyden (66)
Merkley (59)
Casey (56)
Reed (66)
Whitehouse (61)
Johnson (70)
Leahy (76)
Sanders (75)
Webb (70)
Warner (62)
Murray (66)
Cantwell (58)
Rockefeller (79)
Manchin (69)
Kohl (81)
Governors:
Beebe (70)
Brown (78)
Hickenlooper (64)
Malloy (61)
Markell (56)
Abercrombie (78)
Quinn (68)
Beshear (72)
O'Malley(53)
Patrick (60)
Dayton (69)
Nixon (60)
Schweitzer (61)
Lynch (64)
Cuomo (59)
Perdue (69)
Kitzhaber (69)
Shumlin (60)
Gregoire (69)
Cabinet:
Hillary Clinton (Senator)
Timothy Geithner
Eric Holder
Ken Salazar (Senator)
Tom Vilsack (Governor)
Gary Locke (Governor)
Hilda Solis (Representative)
Kathleen Sibelius (Governor)
Shaun Donovan
Steven Chu
Arne Duncan
Eric Shinseki (General)
Janet Napolitano (Governor)
Generals:
Wes Clark
David Petraeus (Dem?)
Stanley McChrystal