Trying to defuse a political a firestorm on Capitol Hill, the founder of an anti-incumbent political committee said Tuesday that his group will agree to designate $25,000 from House Majority Leader Eric Cantor (R-Va.) as a donation for one Illinois primary last month.

The contribution has become a source of embarrassment for Cantor because the group is is taking advantage of new fundraising rules to target incumbents for defeat, including some Republicans whom Cantor supports.

The Campaign for Primary Accountability, a super PAC, plans to file paperwork this month with the Federal Election Commission clarifying that Cantor’s donation from his own political action committee was intended only to support Rep. Adam Kinzinger, a freshman who ousted Rep. Don Manzullo in a primary that resulted from the decennial redistricting process.

The group, founded for the sole purpose of defeating entrenched incumbents from either party, was not asked by Cantor to classify the money in this manner but did so because that was how he wanted it spent. The money — along with a donation from a PAC supporting Rep. Aaron Schock (R-Ill.) — already had been spent on a final flurry of campaign ads that the super PAC bought to fight Manzullo, a 10-term congressman.

“We’re going to report it that way, because that was the intent,” Leo Linbeck III, the founder and primary source of funding for the Campaign for Primary Accountability, said Tuesday in an interview. “The money that Cantor put in got spent on that race.”

This is the latest development in an odd story that began March 16, the Friday before Illinois’s March 20 primary, when the Houston-based organization received a $25,000 wire transfer from a group it had never heard of: the Every Republican Is Crucial PAC. Or, in Beltway-speak, EricPAC, for Cantor.

Linbeck and his advisers had just talked to some wealthy donors in Illinois who vowed to pull together $100,000 for a final “surge” of negative ads against Manzullo. So, he said, he assumed the donation was from an Illinois group. “We kind of figured it was associated with this play, but we didn’t know who was behind it,” he said, explaining that no one from Cantor’s operation ever contacted his group and that he had never met the majority leader.

“He couldn’t pick me out in a room of two,” Linbeck joked. If Cantor or a political associate had called to inform him that the money was intended to help Kinzinger, the group would have told him that it was already on its way to the newly drawn district in Chicago’s exurbs.

Until a reporter from Roll Call, the Capitol Hill newspaper, contacted his staff Friday, Linbeck had no clue that Cantor played any role in his group’s effort to oust Manzullo. He blamed Cantor’s staff for handling the situation in a clumsy manner.

Linbeck’s latest comments provide some political cover for Cantor, who has said he made a onetime donation not meant to go toward other races in which GOP incumbents were targeted.

In a statement, Ray Allen, Cantor’s top political adviser, said: “On Thursday, March 15, 2012, Leader Cantor was asked by Congressman Schock to contribute to an organization that was supporting Adam Kinzinger in the Illinois election of March 20. EricPAC subsequently made a contribution with the understanding that those funds would be used only in the effort to support Congressman Kinzinger. Leader Cantor does not support the actions of this organization in any other election.”

In some corners of the House Republican Conference, Cantor crossed a line merely by donating to Linbeck’s group, which has helped knock out two GOP incumbents and has targeted several others with hundreds of thousands of dollars in negative advertising. The group has been given the equivalent of a scarlet letter designation by both parties’ campaign committees on Capitol Hill. The National Republican Congressional Committee, the House GOP’s campaign arm, has told consulting firms that working for the group would mean that they cannot do business with the NRCC.

The contentious Manzullo-Kinzinger primary, pitting a low-profile longtime congressman against an up-and-coming freshman, roiled the House Republican Conference as a generational matchup. Many junior Republicans poured cash into Kinzinger’s coffers and veterans donated to Manzullo. Every member of the GOP leadership team steered clear of making an endorsement because of the political sensitivities, except for Cantor, who backed Kinzinger. Former Cantor aides, at a separate PAC, aired $50,000 worth of radio ads on behalf of Kinzinger.

Manzullo was furious at Cantor in the final days of the campaign, questioning whether he should resign from the leadership. In an interview just before the primary, Manzullo was asked if he is friends with Cantor. “Not now,” he replied bluntly.

Manzullo appeared to edge ahead of Kinzinger about 10 days before the election, painting himself as the outsider despite his nearly 20 years in Congress. Then, he was hit with more than $220,000 in negative ads, phone calls and mailings by the Campaign for Primary Accountability in the final week of the race. He lost by 10 percentage points, in an election in which 84,000 votes were cast, the highest turnout of any congressional primary in Illinois.

Trying to get ahead of the anger, Cantor began making calls late last week to Republicans who have been or will be targets of Linbeck’s group, according to aides familiar with the discussion. Reps. Spencer Bachus (Ala.) and Jo Bonner (Ala.), for example, were on the receiving end of more than $350,000 worth of negative campaigning by the group, according to FEC reports. His ads labeled Bachus “a debt-raising, status-quo politician” who is under investigation.

Both survived their primaries, barely clearing the 50 percent threshold that prevented them from having to go to a run-off campaign. Rep. Jean Schmidt (R-Ohio) lost her primary after a $150,000 negative campaign by Linbeck.

Cantor’s explanations for the donation have somewhat further confused the issue. At times Cantor allies have suggested that the contribution was a staff error for not properly vetting the group or that it was Schock’s fault for not informing Cantor about the group’s mission.

Linbeck chuckled at those suggestions. “We haven’t exactly been hiding. If they missed that, they haven’t been reading the front page of The Washington Post,” he said, referencing a prominent story about his group a week before Cantor made his donation.

The group is now targeting Reps. Tim Murphy (R) and Tim Holden (D) in the April 24 Pennsylvania primary, with up to 10 more incumbents from both parties targeted in May primaries in North Carolina and Texas. Of the first $1.8 million the group raised last year, more than two-thirds of it came from six-figure donors such as Linbeck, who runs a construction company that his family has operated for decades. Linbeck said he has given more than $1 million for the effort.