It's not merely that conservatives are better at selling their product, or that they happen to have an easier-and undoubtedly simpler-ideological product to sell. It's that they know what they are selling. Liberals in general and Obama in particular cannot say the same.
Editing yourself is like an irksome coin toss. You've got to strip yourself of super ego and operate from the id. Maybe I've got my Freud mixed up. It's just hard to trade a beauty shot for the performance with truth and a brightly lit zit.
It is the emergence of mass media which makes possible the use of propaganda techniques on a societal scale.