All the cool kids are discussing voting and irrational voters and the fact that no single vote ever decides anything. (I once had a law professor who put it this way: My chances of getting hit by lightening while walking to the polling place is greater than the chance that my vote will matter, so voting is suicidal.) These discussions seem to break down into two different positions, both of which I always thought were platitudes: that the people decide things correctly and that the point of voting is to make sure that your point of view wins.
The point of voting is to create and demonstrate the consent of the governed to the legitimacy of the government.
The idea that the people, through voting, can pick out the best policy on some complicated technical issue is just nuts. I believe in the special providence, but I don't think we're supposed to rely on it to that extent. The voters are good, though by no means perfect, at choosing the better person but, more often than not, the issues we think are important in the run up to the election are not the issues that we end up obsessing over during the term. No one asked Bush or Gore what they would do after terrorists flew hijacked airplanes into the Twin Towers and the Pentagon. Immigration was an issue in the 2004, but not much of one. And, as my law professor pointed out, the outcome is going to be the same regardless of whether I vote.