(Graph: Ezra Klein)

But you have to keep Romney’s audience in mind.

In Friday’s Wall Street Journal, Kimberly Strassel criticizes Romney because he “wants Americans to know that he is in the tank for the middle class.” Romney “is following Democrats down the class-warfare rabbit hole,” she writes. “These are mistakes Ronald Reagan would never have made.”

In Forbes, ex-Reagan administration official Peter Ferrara puts the same point more strongly. “Cowed by President Obama’s class warfare rhetoric, Romney promises to eliminate taxes on capital gains, interest, and dividends, only for middle income Americans,” Ferrara writes. “He says he would do that because they were the ones most hurt by the recession, not the wealthy. But effective tax policy does not distribute tax cuts based on who ‘needs’ a tax cut the most. That is Obama neo-socialist class rhetoric.”

Put differently: In elite conservative circles, Romney “is following Democrats down the class-warfare rabbit hole” with an economic plan based on “Obama neo-socialist class rhetoric.” Recall, again, that Romney’s plan extends all the Bush tax cuts and then piles another tax cut that would substantially tilt toward the wealthy on top. The simple fact that he’s attempting to sell it as a measure for the middle class is, in these conservatives’ minds, a betrayal.

I largely agree with Ross Douthat that liberals are overstating the degree to which the Republican primary battle is hurting Romney. But this is a more concrete cost. Romney has been lured into offering a very large tax cut for the top one percent at a time when Americans are very supportive of the opposite: increasing taxes on the top one percent. Whatever you think of the economics of the two positions, Romney’s tax plan is going to make life a lot harder for him in the general election. But it’s a tax plan that he had no choice but to offer, and in fact a tax plan that may yet prove to be too moderate for a significant portion of the Republican base.