When they don't - invoke Harry S. Truman.
Political polls are the proverbial tea leaves of political campaigns and become news stories in their own right. Political polls are difficult creatures particularly in Presidential Elections because the Electoral College System narrows the focus down to 18 swing states - five of which lean Democratic and five lean Republican. National Presidential polls are, if not worthless, very limited in value because we do not elect the President based upon a national vote - something Al Gore ruefully notes at most speaking engagements.