I think Bill Richardson will win the Democratic nomination over Hillary. I'd guess the best Rep. to oppose BR would be Romney - BR takes NM, Az, Co from the Reps, MR takes Mass, NH, maybe Conn from the Dems, & fight in Ohio & Fla decides election again. Governors win these elections, not senators (or cabinet members).
Ooh I hope its not Mitt Romney [shudder]
He's so liberal he's practically a Dem.
I don't think he has very much of a chance in the Republican primary, though he probably would do well against Richardson in an election, as you said.