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During the 2000 Republican presidential nomination, John McCain opened up a brief violent fissure by assailing George W. Bush’s plan to cut taxes. McCain began by arguing that it was more prudent to use the temporary budget surplus to reduce the national debt, but he soon began making the case in moral terms, citing the widening gap between rich and poor and insisting it was wrong to cut taxes for the rich. Right-wingers were apoplectic, and even McCain’s GOP allies were shaken. Before that moment, McCain had been a largely conventional conservative with a handful of apostasies, and his campaign little more than an irritant. His populist opposition to the Bush tax cuts marked him as a full-fledged heretic and united the party Establishment against him in full fury.

There is an echo of this episode in the current fight over Bain Capital, the heart of which is this highly effective and even moving half-hour propaganda film detailing the victims and costs of Romney’s business career. It is not exactly the same thing. The fight is over biography, not policy, and, in this case, the Establishment candidate actually has less right-wing policies than the insurgent. (Though Romney’s program is more right-wing than Bush’s was.) But the dynamic is that the underdog insurgents are exploiting a rift between the Republican elite, which is worshipful of the rich, and the Party’s voters, who view the rich far more suspiciously.

Romney’s official line is that a huge debate over the human impact of his tenure at Bain Capital is a wonderful thing — a debate over free enterprise that he wants to have with Obama and is sure to win. But Republican behavior suggests it’s all a bluff. Even perpetual Republican Pollyanna Fred Barnes expresses his fear today that Gingrich has opened up a deep wound in Romney’s public image. Romney allies are applying intense pressure on Gingrich to ix-nay the ain-Bay.

The GOP Establishment’s deepest and most recurrent fear is an open debate over economic class. This is not a debate they feel they can win even among Republican voters, a majority of whom actually favor higher taxes on the rich. Romney’s assertion yesterday that economic inequality should not be discussed, or should only be mentioned in “quiet rooms,” is a too-frank expression of the GOP elite’s actual belief that the issue must be kept out of political debate.

President Bush’s former press secretary Ari Fleischer, who saw class warfare under every rock, was asked at a 2001 press conference if it inherently constituted class warfare to question any aspect of the distribution of Bush’s tax cuts:

Q: Does he believe that those who don’t like the mix of the different tax brackets that he is proposing are engaging in class warfare? MR. FLEISCHER: Well, there is a — there is always an endeavor in this town to deny tax relief to people, because they accuse some people of being rich or successful, and therefore they’re not entitled to tax relief. And that’s just not a view that President Bush holds. We shouldn’t split people by class. We shouldn’t split people on the basis of success or not success. All income taxpayers deserve tax relief, and that’s why the President’s proposal addresses it for one and all. Q: Well, let’s say that one of the opponents believes, okay, the size of the tax cut’s about right, but I just think — and I’m for the idea of having four brackets as opposed to five, it’s fine — but I just don’t think the particular levels he’s chosen for those four — is he still engaged in class warfare? MR. FLEISCHER: I think if someone were to make a rather economic, esoteric, scholarly argument like you just did, that wouldn’t be class warfare.

“Esoteric, scholarly” captures the same idea Romney is attempting to invoke with “quiet rooms.” Republicans believe any discussion of the disparate class impact of regressive policies constitutes an impermissible attack on the rich. If the matter is to be discussed at all, it must be under conditions that insulate it completely from the political debate, so as to avoid waking up the populist demons.

The irony is that, unlike the Democrats’ line on taxes (rich people are swell but the fiscal trade-off of keeping their taxes low is not worth it), Gingrich’s assault on Romney actually comes pretty close to a plausible definition of class warfare. If you try to define even mild objections to regressive policies as vicious class warfare, you have little room to object when the real thing arrives.