All the votes in the 2012 presidential election have been counted, but one aspect of the race will continue to linger for some time: legal challenges to the way third-party groups spent money during the campaign.

The watchdog group Citizens for Responsibility and Ethics in Washington, or Crew, filed the latest salvo in that battle Thursday with a complaint to the Federal Election Commission, and a corresponding letter to the FBI. The group takes issue with spending by Crossroads GPS, the conservative nonprofit started in part by former Bush administration political director Karl Rove.

Although the Supreme Court’s Citizens United ruling made clear the legality of unfettered interest group spending, advocates for tighter regulation of money in politics continue to press politically active organizations to disclose their donors.

The Crew complaint focuses on comments made by Rove at a secret fundraiser for Crossroads, as recounted by a Bloomberg News reporter in attendance. At the event, Rove was quoted as saying that a donor had provided $3 million for the Ohio Senate race out of affection for the Republican candidate, Josh Mandel.

Crossroads GPS is required to disclose sources of its money to the FEC if the donors earmarked their funds for specific advertisements. In this case, the difference may turn on whether the donor mentioned by Rove gave instructions for specific ads or whether he was only picking the race. At the fundraiser, several advertisements were shown to potential donors, according to Bloomberg.

“Karl Rove and Crossroads GPS didn’t just skirt around the edges of the law,” Melanie Sloan, Crew’s executvie director, said in a statement announcing the complaint. “This time it appears they jumped headlong into a criminal conspiracy.”

Crossroads spokesman Jonathan Collegio dismissed the effort as “your average run of the mill Crew complaint.” Indeed, advocates have filed numerous complaints against the group with the FEC, the FBI, the Department of Justice and the IRS – all to no apparent effect.

“Crew is a hyperpartisan, labor-funded front group that files frivolous complaints like this as part of its mission,” Collegio said. “Crossroads is aware of the laws governing the groups and follows all of them closely.”

Crew often cites lapses by Democratic lawmakers in its ethics reports as well, some of which have been cited by Crossroads in attack ads.

After the 2004 race between George W. Bush (R) and Sen. John Kerry (D), the FEC spent years investigating interest groups which spent more than $200 million on the race. Years later, the groups negotiated a settlement with the commission and agreed to pay hefty fines, although small compared to the amounts they spent on politics.

Figures from media buyers show that Crossroads GPS spent $11.5 million on television advertising in Ohio, while its sister group, the donor-disclosing American Crossroads, spent nothing.

The FEC is perhaps best suited to deal with the matter of donor disclosure, but Republican members of the commission have set a tough standard when considering whether to open similar investigations.

In 2010, they decided not to investigate a similar matter involving a Crossroads predecessor, saying that the New York Times article cited did not contain “specific facts from reliable sources.”