As Newt Gingrich and other GOP candidates viciously attack Mitt Romney for his work at Bain Capital, I’ve been waiting for the other shoe to drop — because as I wrote yesterday, rapacious no-holds-barred capitalism is a core right wing value, and these attacks are basically a repudiation of everything the Republican Party stands for.

And now, here’s that other shoe.

The assault on Mitt Romney’s record as a private equity investor—led by, of all people, Newt Gingrich—has one influential Washington special interest group screaming “enough!”

That would be the Club for Growth, the conservative anti-tax advocates, who Monday released a statement decrying Gingrich’s attack on Romney’s work at Bain Capital as, well, un-Republican.

“Newt Gingrich’s attacks on Mitt Romney’s record at Bain Capital are disgusting,” the group’s president, Chris Chocola, a former Indiana congressman, said. “There are a number of issues for Mitt Romney’s Republican opponents to attack him for, but attacking him for making investments in companies to create a profit for his investors is just wrong. Because of the efforts of Bain Capital, major companies like Staples, Domino’s Pizza, and the Sports Authority now employ thousands of people and have created billions in wealth in the private economy. Attacking Governor Romney for participating in free-market capitalism is just beyond the pale for any purported ‘Reagan Conservative.’ Newt Gingrich should stop his attacks on free markets and apologize to Governor Romney for them.”