Aided by the Supreme Court's "Citizens United" decision allowing unlimited and secret corporate political spending, third-party groups (see that anti-Dahlkemper ad we posted just a few minutes ago) have spent more than $100 million this election cycle -- twice as much as they spent four years ago, and most of it on behalf of Republicans, the NYT reports in a must-read story today.

No group has been more active than "Americans for Job Security," which began running the vicious ad locally against Jason Altmire just yesterday, comparing him to a thief who breaks into your house and steals your wallet and car. AJS is tied to Karl Rove and other George W. Bush advisors and officially staffed by only one person, a young man who got his start by running an anti Hillary Clinton Facebook page.

The list of who's bankrolling their millions of dollars in spending against Democrats is shrouded, the NYT reports:

Because Americans for Job Security was formed as a tax-exempt business league — known as a 501(c)(6) in the tax code — it does not have to report its sources of income. Federal election rules, though, require that when a group accepts a donation earmarked for an electioneering ad, the donor must be identified.

Americans for Job Security avoids disclosure by reporting all its revenue as “membership dues.” It claims more than 1,000 members. But a review of its tax returns shows membership revenue fluctuating wildly depending on election cycles — similar to the fund-raising of political committees that escalates during campaign season.

Click the NYT graphic above for a bigger version.