John Podhoretz writes a 2008 Hillary Clinton presidential run would open the door for a Jeb Bush candidacy:

“With a candidate named Bush running against a Democrat whose name was anything other than Clinton, Democrats would be able to win almost solely on the grounds that America shouldn't be a hereditary monarchy. But with a candidate named Clinton, Democrats would lose that issue against Jeb Bush.”

Podhoretz observes that with this hurdle cleared, Bush has nearly all the elements necessary for a successful run, something much of the 2008 field on its surface lacks.