Richard Martin, who oversaw Claire McCaskill's winning U.S. Senate race in 2006, said today he's formed a new SuperPAC aimed at competing with the squadron of groups taking aim at McCaskill.

Martin is treasurer of the pro-McCaskill "Heart of America" PAC. He said he's raised about $100K so far.

That's a lot of money, but it appears to pale in comparison to all the bucks spent by groups such as Karl Rove's Crossroads PAC that's been spending aggressively against McCaskill on TV ads.

"Even if it’s just a fraction of what Karl Rove does, I want to combat some of that," Martin said.

There's one other difference. Martin pledged to disclose the names of donors to the Heart of America PAC even though he's not required to do so under new federal campaign rules. Rove's PAC does not disclose its contributors.

"We believe in 100 percent transparency and call on all SuperPACs to do so," Martin said. "Missouri voters deserve to know who’s behind all the ads trying to influence outcome of a very important election.”

McCaskill issued a statement saying she also backed the need for full disclosure.