Tim Kaine, a Democratic candidate for the U.S. Senate in Virginia, called on his would-be Republican rival, George Allen, to mutually agree to disclose the donors to any outside groups spending in the fall campaign, including the super PAC that was formed to support Allen.

Allen’s response: No thanks.

It’s not the first time Kaine has tried to lure Allen into a truce. During last December’s debate, Kaine said he would tell outside groups friendly to Democrats to stay out of the race if Allen would do the same with his allies.

Allen refused, but said, “I like Virginia's approach, Virginia laws that are based on full disclosure and freedom.”

Kaine jumped all over that comment and attempted to hold Allen to it after Politico reported Monday that a well-connected Republican started a Super-PAC intending to throw $2 million to $3 million into the race. Kaine asked Allen to pledge that there would be no secret money influencing the election and any groups wishing to weigh in should reveal their financial backers.

“With secret money out of our race, Virginians will be assured of a transparent campaign instead of one dominated by secret special interests who are afraid to face public scrutiny,” Kaine said.

Allen called it an “unfortunate gimmick” and rejected the offer.

“It's difficult for voters to take talk of transparency seriously when it comes from a campaign that is substantially funded by big union bosses and their organizations,” Allen wrote.