That’s the design rankings of candidate sites according to the accumulated ratings of pages tagged “election” at CommandShift3 (the Hot or Not of web sites):
According to CS3’s Amit Gupta, these are cross-site rankings (i.e. most of the battles occurred between an election-tagged site and a site tagged something else) which might eliminate some of the political bias you’d expect.
Keep in mind that, like Hot or Not, these ratings measure the superficial look of the contenders, not any sort of real substance. The most functional sites probably don’t win a lot of sleek home page contests.