I'm not a huge fan of the various political blogs and sites as most of them don't offer much except ad hoc opinion and the opportunity to express even brasher ideological assertions, which we already have plenty of.
All the more reason put in a plug for fivethirtyeight.com (538= number of delegates in the electoral college) which I and most of my media-junkie friends are obsessed with. It's run by Nate Silver, who seems to make his living analyzing and modelling baseball statistics. But you don't have to be a fantasy-baseball freak to see that he's taking quant to a whole new level here, aggregating a dozen diffrent polls on a daily basis and then analyzing the results, weighting the polls based on a number of factors, including past accuracy. He also calculates a win/loss percentage based on 1,000's of simulations of potential outcomes. In fact, the rigor, depth and insight of the analysis puts most of the market research analysis I've seen--and I've seen a lot--to shame. Maybe we should start scouting the fantasy baseball leagues for talent. Check it out.