The only Republican candidate I’ve heard of that could win in 2012 is Romney; the others are too far right. (But then, we thought Obama was too far left; thee MSM convinced enough voters otherwise.)
And even then, it is hard to defeat an incumbent. I really don’t want to wish on the country the kinds of things that would assure a Republican victory; I am thinking of the way things were under Carter. Or worse, a nuclear terrorist attack on the US, G-d forbid.