The watchdog group Citizens for Responsibility and Ethics in Washington has filed a complaint with the FEC over a $25,300 donation by Senator Mary Landrieu’s campaign to the U.S. Treasury.

CREW executive director Melanie Sloan argues, “We all know politicians don’t give up campaign contributions – much less $25,000 – without a very good reason. It appears Sen. Landrieu’s reason may have been to avoid a scandal or, even worse, a federal investigation into some of her contributions.”

Marc Elias, Senator Landrieu’s campaign lawyer, called the lawsuit “frivolous” and said the campaign wanted to protect the identity of donors who “may not have done anything wrong.” The CREW complaint however argues that the only two scenarios in which “dirty” money may be donated to the Treasury are if a donor is under a Justice Department investigation, or has been convicted for making illegal contributions. In both of these cases, the identity of the donor must be made public.

Sloan follows up, “Our campaign finance laws were designed to ensure transparency. If Sen. Landrieu did nothing wrong, she has no reason not to come clean with the American people and explain why she turned over $25,000 in contributions to the Treasury.”

The Landrieu campaign will have 15 days to respond after the FEC provides its formal notification.