America’s corporations and their executives are in grave danger, warns Mitch McConnell, the Senate Republican leader. According to Mr. McConnell, if President Obama were to find out who was giving hundreds of millions to secretive groups running political attack ads, he would “punish and intimidate” them with all the governmental tools at his disposal.

This is not one of those laughable Internet conspiracy theories. The senator actually wrote this in an op-ed essay in USA Today on Thursday as his explanation of why the Disclose Act, which would end the practice of secret political donations, is “un-American” and an attempt to limit free speech.

The vast majority of the secret money going into “social welfare” organizations like Crossroads GPS, founded by Karl Rove, is being spent on behalf of Mitt Romney and other Republican candidates, and the Disclose Act is coming up for another vote in a few weeks. So Mr. McConnell needs a new excuse for filibustering it again. But his suggestion that President Obama and Democrats want disclosure in order to compile a list of “enemies” is repugnant.

Corporations love the secrecy provided by Mr. Rove’s group because it protects them from scrutiny by nosy shareholders and consumers. They want a big influence on elections, but without leaving any tracks. People who give directly to political campaigns or super PACs know their donations will be public, and know that disclosure is part of participation.