...I think he's the most progressive of the three...
In other words, Jeb is not enough of a wingnut to satisfy uber-right wing voters.
I will admit, he is way smarter and more capable than Dubya was. But what will hold him back is the Bush name and the fact that he is a bonafide Neocon. Jeb Bush was a member of the Project for a New American Century (PNAC), as were such notables as Dick Cheney, Donald Rumsfield, Paul Wolfowitz, among others.
Hopefully, being associated with that crew will taint any possibility of him running for president. Electing Jeb Bush opens the door to reinstating the Neocons in high-places within our government, and that will lead to newer and more vigorous wars than we have been fighting since 2001 (hey and maybe even newer "New Pearl Harbors" to get the people behind their plans for conquest).