If Elizabeth Warren beats Scott Brown on election night 2012, the 2016 buzz will begin the next morning.
Warren's a no-brainer to get the convention keynote. I assume she'll hit it out of park and, given Obama's own path, the chatter will start then and there.
Cuomo and Warren will be the two the media initially focus on throughout the 2nd term (ala Romney and Huckabee) this past cycle, but I definitely see somebody like Schweitzer make some noise very early and quickly rising to the top tier.
Romney and Huckabee? You're leaving out someone the media focused on for a while, no? But perhaps Christie is a better comparison than Palin. I doubt they'll let Hillary say "no" less definitively or fewer times than they forced Christie to. Speaking of him, Schweitzer has a similar plainspoken appeal, albeit Western instead of Jersey. But he may not have the vacuum that almost sucked Christie into the race. Also Biden seems to be interested and will be able to get himself chatted about.
O'Malley and Warner are sort of intriguing, but I just don't think they have the pizzazz to make it all the way.
Like trying win at Antietam.
If Feingold runs he will immediately start off with a good chunk of solid support that will be sustained throughout, but I'm not sure if it goes much beyond that-- ala Ron Paul.
But Feingold would have a much higher ceiling than Paul who is anathema to a majority of his party.