according to polls (though of course they are not too predictive as we have seen) McCain is the only one who keeps it competitive (within one or two points on either side). as much as we dont like him (and before anyone goes batty with me i voted in NH for Fred) he does seem to appeal to the squishy middle and some Democrats. this is the rationale for why he has a better shot to win.
McCain can appeal to the squishy middle all he wants, but unless he has the base he will lose. Think about it...the last few elections have come down to 0-3% differential between the winner and loser. Hillary or Obama would at least have the liberal base and would really be fighting for the independent vote. The independents are going to pretty much split down the middle between Republican and Democrat. McCain is already at a disadvantage because if he even loses 2% of the conservative base vote, he loses the election. I think he’ll lose more than 2% based on how much conservative voters hate him. They’ll stay home on election day.