We could argue this point.Look back in history to see how Adolf Hitler rose to power ... I don't believe most of his early supporters would have elected him if they knew what he was really capable of.
Hitler wrote Mein Kampf in 1924 and it became a bestseller before he got into power in 1933. I've never read that book, but from all I know Hitler clearly outlined his political ideology, gave a lecture on "the Jewish peril" and openly stated the future German expansion in the East. So I think people knew quite well what he stood for.