Americans for Prosperity launching major ad campaign

Washington (CNN) - The conservative, nonprofit advocacy group Americans for Prosperity (AFP) is buying more than $20 million for commercials in 11 key battleground states, a Democratic ad buying source confirmed to CNN on Thursday.

The group, partially funded by the influential Charles and David Koch, is one of the major players when it comes to the ad wars this campaign season.

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The buys are being made in Colorado, Iowa, Florida, Minnesota, Nevada, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin, according to the ad source.

The group refused to comment on the ad buy, which was first reported by NBC News.

AFP, which has spent more than $12 million this election cycle, ran ads this summer against the Obama administration's health care initiative after the Supreme Court upheld it, as well as several million dollars worth of commercials against Democratic Senate candidates in six states: Florida, Missouri, Montana, Nevada, Virginia and Wisconsin. In June it also launched a $5 million ad campaign in six states trying to capitalize on the comments made by the president that the private sector is "doing fine."

Besides AFP, other major Republican groups are expected to spend hundreds of millions of dollars. American Crossroads, co-founded by Karl Rove, and its non-profit affiliate, Crossroads GPS, are expected to raise at least $300 million this cycle, sources have told CNN, while the super PAC backing Mitt Romney, Restore Our Future, hopes to raise more than $50 million.

This comes as the Democratic-leaning super PAC Priorities USA Action had spent $15 million for the year as of the end of June, but its fund-raising is picking up. The group is reserving $30 million for ad time for the fall, sources told CNN.

- CNN Political Editor Paul Steinhauser contributed to this story.