I disagree with Sam's view on voting. I think I might be more Popperian than Sam, in that I never expect to find a candidate whose views correspond with mine. We're all different, and the best I can hope for is some agreement. That's not why I vote. I vote to turf out, or keep out, the bad guys, the ones I don't want to see holding office. This follows Popper's view that democracy helps us to prevent bad or incompetent rulers from doing too much damage.
I could take the position that even if I don't vote, other people will do that job for me, so I can save myself the inconvenience and free-ride on their efforts. I know that many critics of free-marketeers accuse us of acting only in self-interest, but many experiments in game theory situations show that the default position is not selfishness but co-operation and goodwill if others reciprocate.
I'm happy to go along and co-operate with my fellow electors in trying to turf out, or keep out, the bad guys. In the election for London Mayor I regard one of the front runners as well worth keeping out, and will vote accordingly, hoping that enough of my fellow electors do likewise.