Of 43 presidents, only Kennedy and Harding moved directly from the Senate to the White House. Of the 54 presidential elections, only 15 were won by current or former senators. Voters in presidential elections historically prefer candidates with executive experience, usually governors.

So where does that leave us with the current slate of candidates? Richardson is the only Democratic candidate with executive experience and he's not the likely nominee. On the Republican side there's Giuliani, Huckabee and Romney. All have a shot. So, unless McCain gets the Republican nomination, it looks like it will be a Democrat with only Senate experience running against a Republican with executive experience.

No one likes historical determinism in politics but past trends favor a Republican in 08. Of course nothing is written in stone. There are three very strong candidates - all current or former senators - running on the Democratic side and maybe we're due for an exception to the rule.

And, there's Bloomberg, who could really throw a monkey wrench into the historical record if he decides to run.