New independent circulation numbers show a sharp decline in readership of Politico and other left-leaning news websites, an ominous trend for the suburban Virginia-based news outlet and its peers as Americans head into an election year. Recently published and publicly available Web traffic data indicates that “unique visitor” traffic to politico.com in November 2011 was 15 percent lower than in the previous month, and 31 percent lower than in November 2010. The data, from Compete, Inc., also show an overall two-year decline. Political websites gain and lose readers throughout election cycles, with presidential election years trending higher in unique Web...