Bottom line is, Andrew and Caroline notwithstanding, Rudy is electable and Hillary and Obama are not, especially if they continue to cannibalize each other's base.
However, if a surprise entry such as Al Gore were to enter the fray, the mix would be different and unpredictable. We would have to poll like crazy to determine the effect. Just IMHO...
Al Gore will change nothing. Didnt you see that just last week he was exposed as a fraud and a charlatan?
How is Obama not electable? He's charismatic and a smooth operator to say the least. He hasn't taken Hillary's bait, the press adores him, and he's playing this "optimism" thing up quite well. On top of that, he's black, which makes him bulletproof in a lot of ways with the media.
I'm just saying the GOP is going to have to have one heck of a charismatic character to take him down. I think Giulani could stand well with him, though I think Romney would be even better.