Conservatives are furious with GOP candidates like Newt Gingrich and Rick Perry for attacking Mitt Romney’s Bain tenure as capitalism run amok. Gingrich has claimed that Bain “looted” other companies, and Perry today slammed enterprises like Bain as “vultures” who “eat the carcass” of its victims, prompting a fresh round of outrage from the right.

Conservatives have good reason for being angry about this. In attacking Romney’s Bain years in these terms, his fellow Republicans are mainstreaming and giving bipartisan legitimacy to one of the chief arguments Obama and Dems will use against Romney in the general election. They are badly undermining Romney’s whole pushback against it — giving Dems an advantage in the coming war to define Romney’s Bain years, which will be as central to the general election narrative as the war over John Kerry’s Vietnam service was in 2004.

Consider: The chief argument Romney has made against Dems attacking his Bain years is that they are attacking capitalism itself — they are putting “free enterprise on trial.” The point of this argument is to distract from the case Dems are making — that his Bain years are emblematic of a brand of predatory capitalism that’s rooted in putting profits first and is ultimately a destructive force. Romney’s pushback is designed to cast the Dem attacks as anti-business and out of step with the foundations of American life, as proof that Dems don’t understand how the private sector really functions — something that could have appeal to voters who are fed up with government’s failure to fix the economy.

But now you have the other leading Republican candidates on the record directly rebutting the claim that the Dem argument is anti-capitalist.

For instance, Gingrich today argued: “Show me somebody who has consistently made money while losing money for workers and I’ll show you someone who has undermined capitalism.” And Perry, in addition to deriding Bain as a “vulture,” has also described Romney as a “buyout tycoon who executed takeovers, bankrupted businesses, and sent jobs overseas while killing American jobs.” It’s same to assume Perry didn’t mean this as a compliment.

As Steve Benen notes, this is all a sign of how much the debate over free enterprise has shifted: “For all the talk about this being a center-right nation, there’s a realization that Americans are uncomfortable with excessive greed and the kind of ruthless, screw-the-workers style of capitalism Romney used to get rich.”

I’d go even further. This general election will turn heavily on a battle over the two candidates’ visions of capitalism and the proper role of government in regulating it. Yet the leading GOP candidates are on record arguing that Romney’s practice of it — which he regularly cites as proof of his ability to create jobs, as a generally constructive force and even as synonymous with the American way — is not really capitalism at all, but a destructive, profit-driven perversion of it. Thanks to them, this is no longer a left-wing argument. As the GOP candidates have themselves confirmed, this argument reflects concerns about Wall Street excess and lack of accountability that are thoroughly mainstream, and you’ll be seeing plenty of footage of these Republicans making it in battleground states this fall.