Van Hollen aide calls out Chamber on Disclose Act

"Our forefathers went to great lengths to protect the right to free speech for everyone," the ad states. "Yet the so-called Disclose Act does just the opposite."

The Chamber contends the bill threatens free speech because it requires public disclosure of chief supporters for political ads. Others say the legislation will intimidate supporters shy about airing their political opinions and stop them from donating to certain causes. These groups have yet to explain how fuller disclosure would intimate donors.

Thornell claims donors who have nothing to hide should not be troubled by the bill.

"It empowers the American people so they know who is spending money on our elections," he said. "It's a tough reform bill and that's why so many special interests hate it."