Republicans on the Federal Election Commission voted to block investigations into two more major political nonprofits that the commission’s own staff lawyers argued broke election law in 2010, according to recently released documents.

Earlier this year the FEC released a general counsel’s report reaching the same conclusion about Crossroads GPS, a nonprofit co-founded by Karl Rove, though Republicans also blocked further investigation in that case as well.

All three cases hinge on who must report their donors. Nonprofits don’t have to say where their money comes from, but FEC staff attorneys have found that all three groups had electoral politics as their major purpose and spent more than $1,000 backing candidates, and on that basis must register as political action committees. That step would require the groups to name their contributors.

In all, the FEC’s general counsel’s office found that Americans for Job Security had spent $9.5 million on federal political ads in 2010, which amounts to at least 76.5 percent of the groups budget for that calendar year, and the second group, the American Action Network, spent at least $17 million, or about 62.6 percent of their spending.

Democratic FEC commissioners decried Republican’s unwillingness to even look into the allegations, stating:

Millions of dollars are flowing into our political system–over $310 million in the 2012 federal elections–often to fund aggressively negative ads, without any way for the public to know where the money is coming from. This is not what Congress intended the campaign finance system to do, not what the Supreme Court has insisted should be done, and not how it has long been done at the Federal Election Commission. Disclosure laws provide voters with the information necessary to evaluate the source of political messages. Unfortunately, the Commission has reached an impasse that has prevented us from enforcing the Commission’s own written policy’ – a policy that should shine a much-needed light on the sources of dark money.

Republicans rejected commission lawyers’ interpretation of the law, and sought a much narrower reading of what constitutes election activity when divining a groups’ primary purpose. The differences are legalistic, but boil down to whether “issue ads” that slam a clearly defined candidate for office without directly urging viewers to vote for or against the candidate should be counted as political. FEC lawyers note that this type of ad has been counted against groups in the past, though GOP commissioners discount that.

Both complaints were brought by Citizens for Responsibility and Ethics in Washington, a watchdog group. Adam Rapapport, senior counsel at CREW, said the votes against an investigation relied on an “absurdly narrow” interpretation of what constituted political activity. “We’re disappointed that the three republican members of the FEC are blocking disclosure by some of the biggest dark money groups,” he said.

The American Action Network is registered as a 501(c)(4) “social welfare” nonprofit, and was founded by former Republican Senator Norm Coleman. Americans for Job Security is registered as a 501(c)6 nonprofit business league and was founded in 1997.

It’s hardly the first tangle with authorities for Americans for Job Security. A similar FEC complaint from an earlier political cycle had the same result–FEC attorneys sought an investigation, but Republican commissioners shut it down.

More recently, Americans for Job Security was an intermediary in funneling $15 million in undisclosed contributions related to California ballot initiatives that resulted in a $1 million dollar fine against two other groups involved. AJS escaped without a fine.

In Alaska, AJS agreed to a $20,000 settlement after being accused of funneling undisclosed contributions for a 2008 ballot measure that would block a mine expansion in Bristol Bay. Though the group acknowledged no wrongdoing, a 2009 report from the state’s Public Offices Commission called AJS “nothing more than a sham entity created to allow people… to evade campaign disclosure law.”