I agree with this.
I also think people in positions of public trust--which includes pretty much all elected officials--are held to a higher standard.
Roosevelt and Mitterand have never been considered bad presidents due to extra-marital affairs.
Roosevelt is by many people considered one of the greatest, if not the greatest, American president ever, and one of the greatest politicians and statesmen of all time.
So if McCain is having an extra-marital history or not should not be an issue. He's not in bed with the American people.