A third complaint has been filed with the Federal Election Commission alleging that Crossroads GPS, a group co-founded by Republican strategist Karl Rove, has been unlawfully hiding its donors from the public by masquerading as a “social welfare” organization.

Citizens for Responsibility and Ethics in Washington (CREW) filed the complaint on Tuesday, claiming the pro-Republican group failed to report TV ads it ran against three Democratic Senate candidates to the FEC.

“Crossroads GPS wants to have its cake and eat it too. Karl Rove’s secretive 501(c)(4) wants to run political ads without complying with the disclosure rules applicable to such ads,” said CREW Executive Director Melanie Sloan. “By disguising political ads as issue ads, Crossroads is trying to do an end run around the law.”

Crossroads GPS contends that all its ads are "issue ads," which are “a position statement about, or a discussion of, public issues.” But CREW alleges that the three ads constitute independent expenditures, which are communications "expressly advocating the election or defeat of a clearly identified candidate."

The distinction between issue ads and independent expenditures is an important one. Crossroads GPS is registered with the IRS as a tax-exempt 501(c)(4) organization, allowing the group to raise unlimited sums from wealthy individuals and keep the identity of those donors a secret. But 501(c)(4) organizations are prohibited from campaigning "on behalf of or in opposition to any candidate for public office."

If Crossroads GPS is found be to making independent expenditures, it would be subject to federal reporting requirements like other political committees.

Earlier this month, Crossroads GPS aired an ad that accused former Virginia governor and Senate candidate Tim Kaine (D) of being a "cheerleader for massive spending." The ad urged the residents of Virginia to tell Kaine to "stop backing reckless spending." But Kaine could not do so even if he wished. His term as governor expired in January 2010.

In June, the organization aired an ad that attacked Heidi Heitkamp, a Democratic candidate for Senate in North Dakota, for endorsing President Barack Obama's health care reform law. The ad urged the residents of North Dakota to tell Heitkamp to "support the full repeal of Obamacare." However, she has not held public office since January 2001.

Similarly, in May, Crossroads GPS aired an ad attacking Bob Kerry, a Democratic candidate for Senate in Nebraska. The ad urged the residents of Nebraska to tell Kerry to "support balanced budgets." But as with Heitkamp, Kerry has not held public office since January 2001.

CREW said the "only reasonable interpretation" of the ads is to encourage actions to defeat the Democratic candidates.

Obama campaign chief counsel Robert Bauer and the Democratic Senatorial Campaign Committee have also filed complaints with the FEC alleging that Crossroads GPS has violated the Federal Election Campaign Act.

[Image via Flickr user Sachyn, Creative Commons-licensed]