Thanks to the media, who marginalized him every chance they got.
Who's a more "credible" candidate: a 10-term Congressman who's also an M.D. and was an Air Force Captain, or some kid who has been in the Senate all of 2 years?
More terms in Congress does not mean that he's a better politician. Some people are just naturally better.... like how Bill Gates was a better businessman at 25 than you could ever be.
He is an M.D., so Obama's a J.D. Paul went to Duke (good Southern boy that he is), Obama went to Harvard Law School, and was one of the top students there (a far more competitive place, at a far more competitive time).
Being a flight surgeon serving "outside the Vietnam war zone" doesn't exactly give him military cred, just great benefits.
And really, who cares about experience? THe experienced ones got us here... a greenhorn couldn't do worse.