Obama's got him beat
Fragment of a discussion from Comments:UK elections: David Cameron becomes Prime Minister
Certainly has! (He has beaten Nick Clegg too, who has 5 years experience.)
Actually Teddy Roosevelt had them both beat, He was vice president for just 6 months before assuming the office of president. Before that he had a few very short stints as Governor of New York, Secratary of the navy, and President of the Board of New York City Police Commissioners, among other things