Smears and elections.

All too often we see political candidates smeared, one candidate smearing the other... this is an example of mud-slinging. I've been watching the 08 election and I've noticing a bunch of counteracting forces that are at play. Both candidates try to convince their base that they are right for President by attacking the other candidate. One candidate attacks the other, makes a charge about them, and people react. It creates a frenzy of madness. It seems like nothing in politics is civil at times... when the election comes some people are bitter but that's to be expected. What are we to make of the mass reactions from the general population by these politicians? The general population sometimes sees a like-able politician as an anti-christ, or, a messiah, and, an unlikeable one as a normal politician, and still supports them anyways because that's to be expected in politics. Is there some reason that this mudslinging is so effective in changing people's minds?