Follow the money
opensecrets.org is a great site that exposes political fundraising data in an variety of accessible forms. Go poke around for a little bit. Specific gems I ran across include Missouri’s Senate race was the 2nd most expensive in 2002, and local data includes records of all donations by zipcode (some people I didn’t know the party affiliation of were exposed herein). Depressing is how quickly the amount of money involved has been increasing in recent years, how directly dollars spent and votes received correlate, and how much money pours into state campaigns from outside.