Newt? He used to run congress, is one of the smartest men in all of DC, and had the balls to say the whole lot of Republican contenders in 2008 was weak.
Jeb? By far the most qualified and shrewd, but he is a PNAC author, and he does have the 'Bush' name. Still, people forget.
Mitt? If we're all still in a world of financial hurt after 4 years of depression/recession in 2011, ait's likely a golden boy like Mitt Romney would get some love with his economic prowess.
Palin? 60% of voters felt she was not ready for the VP role, much less President. And 18% of registered repubs who voted in 2004 chose to stay home in 2008. Energize the base? Hard to claim that when 1/5 of your previous voters stayed home and let Obama win.