This story in the Washington Post lists Presidential contenders for '08 who are currently state governors. The advantage governors have over legislators as presidential candidates--lawmakers have lengthy voting records with which to beat them silly. Governors don't. Last November is a great example.
In another Post story Senator Joseph Biden says Hillary would be "incredibly difficult to beat" in '08. While her tenure in the senate has been relatively short, her voting record will be scrutinized. Her voting should be very interesting to watch these next few years.