The watchdog group accused Highway 31 of engaging in a “secrecy scheme to spend $4.2 million in the race” to support the Democratic candidate, AL.com reported.

Part of the complaint is that Highway 31, which is headquartered in Birmingham, said it spent $1.15 million in Alabama’s special election.

Jones pulled off a shocking victory in December against former state Supreme Court Chief Justice Roy Moore amid allegations Moore had inappropriate sexual conduct with teenage girls.

From the Archive: Scenes From Doug Jones‘ Election Night Rally

But while the group said it raised no money, Senate Majority PAC, a Democratic super PAC in Washington, revealed later to The Associated Press that it helped finance Highway 31.

The Campaign Legal Center is accusing Highway 31 of not disclosing Senate Majority PAC’s backing and misrepresenting its donors.

Brendan Fischer, director of federal and FEC reform at the center, accused Democrats of hypocrisy for saying they support transparency but then pushing new legal theories to justify secret spending.

“Despite laws requiring that super PACs disclose their donors, Alabama voters went to the polls on election day without knowing who was backing Highway 31,” Fischer said. “This secrecy scheme cooked up by Highway 31 and its backers threatens to create a new disclosure loophole that will be exploited by billionaires and operatives supporting both parties, unless the FEC does its job and enforces our disclosure laws.”