A conservative group is running a TV ad likening the Democratic district attorney prosecuting former House Majority Leader Tom DeLay (search) to a vicious dog.

District Attorney Ronnie Earle (search) brought charges last month accusing the Texas Republican of illegally funneling corporate contributions to GOP candidates for the Legislature. The charges forced DeLay to relinquish his leadership post on Capitol Hill.

The Free Enterprise Fund, based in Washington, began running the ad in heavy rotation Thursday on Austin TV stations and on the Fox News Network.

"A prosecutor with a political agenda can be vicious," the narrator says, while a snarling dog barks on screen.

Earle's office would not comment on the advertisements, but has denied the investigation is politically motivated.

Free Enterprise Fund spokesman Todd Schorle said the ad campaign may be expanded to other markets around the country.

"We feel that Ronnie Earle wants to obstruct the free-market agenda and he's using liberals to bring the free-market agenda to a halt in Congress," he said.