If Hillary Wins...

There will be trouble on the horizon for Dems... Possible races that I see:

Hillary vs McCain: Right now the RCP head-to-head average has her 4 points behind, losing in 3 of the last 4 polls. On the positive side having McCain in makes it less likely that Bloomberg will come in and grab votes. Only way to win this is the '04 Bush model, rile up your base and rely on turnout to overcome your losses with independents.

Hillary vs Guiliani: Best case scenario for Hillary. Right now the RCP head-to-head average has her 8.7 points ahead (that would probably slim out as Guiliani gets attention from the press.) Guiliani is more polarizing than McCain, but he probably can keep Bloomberg out just by virtue of his history with New York. Both would fight for the middle but Hillary would probably again have to rely on a big base turnout.

Hillary vs Huckabee/Romnee vs Bloomberg - Hill has a lead over both 6.5%/12.4%, but these races leave enough space in the middle for Bloomberg to squeeze in and siphon off anti-Hillary dems/independents.

Regardless of who she faces she has the built in handicap that 43% of the US is unwilling to vote for her. That leaves a pretty slim margin to try and convert.