Originally Posted by Spark
They are, the question is why. A high-quality candidate which the GOP base is firmly behind would be a big favourite to win the election, even accounting for Obama's immense campaigning skills.
Each candidate really gets one shot at winning the Presidency, so you have to pick your moment carefully. If one was serious about running, you had to start laying the groundwork in 2008. Back then, no one could've anticipated that Obama would be this vulnerable come election time. Even with all his vulnerabilities, Obama has a 50/50 shot at winning. That's too high a risk to take for the hot shot candidates you mentioned. They are betting that Obama will win and they will have an open election to contest for in 2016 and hence much better odds.