Government Awareness

I'm thinking about some stuff... haven't come to any conclusions just yet, just making some observations and forming some questions.

Who is it that becomes politicians? What are their reasons for wanting to be politicians? How can we, as voters, know their reasons before putting them into office? Are there any measures already in place to weed out those who want power from those who truly wish to serve the best interests of their nation and all of its citizens?
Have we reached the point where career politicians have replaced the appointing of the best and brightest to civil service? Was there ever a time when this was not the case, or is the idea of politicians motivated by patriotism and chosen by merit merely a sort of early american myth?

I'm rather disturbed the fact that I don't know the answers to so many important questions, nor even have a good idea of where to look for them.

This post was inspired in part by reading this post by tzimiel, found by way of a post by helen99.