iconoclast - eye-KON-oh-KLAST - one who attacks cherished beliefs or institutions
Example: "Ted Kennedy, who died of a brain tumor last night, was known as a political iconoclast, playing both sides to suit his patriotic motives when necessary."
As a starter: and as a former teacher in English, I hope to add to reader's vocabulary by presenting a word a day in simple terms that anyone can understand - from current use in publications, radio,TV, etc. Remember: use a new word three times in a day and it's yours forever!