comScore
New research from comScore shows that "while political blogs and sites may attract a good amount of visitors from across party lines, they are still more likely to regularly engage visitors who share the same views." Among the sites studied, Politico has the most balanced audience with 29 percent of readers identified as Democrats and the same percentage identified as Republicans. Daily Kos has the highest percentage of Independents, 46 percent of their readers. The political affiliation is based on voter registration.

Political news sites draw visitors from diverse political leanings. (comScore chart)

But many sites tend to engage one political ideology much more than the other. (comScore chart)

Huffington Post's Politics section was the most heavily visited of any politics sites in this category, with 9.2 million unique visitors in February. In Sepember, comScore placed HuffPost Politics number one, with CNN Politics second and Politico third among the sites studied then. In this study of February visits to a smaller selection of political sites, Drudge Report was second with 4.9 million uniques, NewsMax sites were third and Politico was fourth.