Polls for American election November 4th 2008

How accurate are polls and what are their purposes if their accuracy is slightly better than random?

Seems to me that polls, when calling a tie, are better for democrats "(liberals)" than for republicans "(conservatives)".

Here is an interesting video about election polls, their errors, and how they are conducted.

Below is our U.S. election poll 2008 please vote.

vote here Presidential election 2008