Political blogs and news sites have seen healthy gains during the 2008 presidential election season compared to a year ago, according to a new study from comScore.

The HuffingtonPost.com led among a group of stand-alone political blogs and news sites with 4.5 million visitors in September, up 472 percent compared to a year ago, while Politico.com attracted 2.4 million visitors (up 344%) and DrudgeReport.com saw 2.1 million visitors (up70%).

“With each new election cycle, the Internet is playing a more significant role in shaping the stories of the day that are so crucial in formulating public opinion on issues and candidates,” said Andrew Lipsman, senior analyst at comScore.

“That most mainstream news outlets now have their own political blogs is a testament to their increasing reach and influence. However, several independent blogs unaffiliated with larger media outlets paved the way in this space and are really beginning to enter the mainstream public consciousness with this current election cycle.”

September was the single biggest month on record for both the HuffingtonPost.com and Politico.com since their launches.

A number of sites focused on political polling also did well. RealClearPoltics.com, which tracks composites of polls by state, attracted 1.1 million visitors in September, up 489 percent over a year a go. Two other polling sites, Pollster.com with 194,000 visitors and FiveThirtyEight.com with 169,000 visitors, also saw notable traffic in September.

The leading conservative blog, FreeRepublic.com, saw marginal declines compared to a year ago, though it sill attracted nearly 1 million visitors in September. Other conservative blogs, such as Newsbusters.org (up 547% to 732,000 visitors), WorldNetDaily.com (up 55% to 636,000 visitors) and MichelleMalkin.com (up 140% to 247,000 visitors) saw solid gains.

Looking at the demographic profiles of the top three sites, HuffingtonPost.com, Politico.com and DrudgeReport.com, revealed that visitors to these sites tended to be older, wealthier, and more likely to be male than the average U.S. Internet user.

Of the three sites, Politico.com skewed the oldest with 23 percent of its visitors age 55 and older, while DrudgeReport.com skewed wealthiest, with 40 percent of its visitors earning at least $100,000 a year, and the highest concentration of males at 57 percent. HuffingtonPost.com, the site with the largest audience, was the most similar of the three when compared to the overall Internet audience.