Oh my goodness, this is so frustrating. Everyone thinks Barack Obama is an ENFx because of what he wrote in 'Dreams from My Father and 'The Audacity of Hope.' The books were written specifically to appeal to (segments of) the population. You can imitate other type patterns' writing, speech, etc. For example, I could write two books in an inspiring, philanthropical ESFJ tone. Instead of writing about my observations of societal problems that no one else seems to notice and explaining the patterns and cycles that are responsible for these problems, I would just tell a story about how I took someone off the street, housed them, baked them cookies, and then they became a model citizen and went off in the world to lead a highly conventional life. Ok, so that's sort of a joke, but the point is that with a little observation and insight into other types, you can masquerade as another type. When I used to work in scientific research, I would always test INTJ.
There are A LOT of people out there (celebrities, politicians) that project a certain image that they know is going to be appealing to the American people. Projecting that image helps them to complete their 'task' more effectively. The only way to accurately type people is to tease out the UNDERLYING patterns in their life: how do they make decisions, how do they behave around other people, how do they solve problems. If you go based on political ideology, public policy, or ideals that people SAY they aspire to, you're going to get thrown off track. In general MBTI describes behaviors and not beliefs.