[Update: On Thursday evening, John Boehner unexpectedly called off the vote on Plan B because he didn’t have enough votes to pass the measure. Some ultra-conservative House Republicans balked at supporting an increase in tax rates even for those earning a million dollars a year or more. Others disliked the bill because it didn’t include any spending cuts. Virtually no GOP members opposed Plan B on the grounds that it was too regressive. Where this humiliating setback for Boehner leaves the negotiations with the White House was unclear. “Now it is up to the president to work with Senator Reid on legislation to avert the fiscal cliff,” a statement from Boehner’s office said.]

Back in November, a week after President Obama’s reëlection, Bobby Jindal, the ambitious young Republican governor of Louisiana, sat down with Politico and talked about the lessons of Mitt Romney’s defeat. “We’ve got to make sure that we are not the party of big business, big banks, big Wall Street bailouts, big corporate loopholes, big anything,” Jindal said. “We cannot be, we must not be, the party that simply protects the rich so they get to keep their toys.”

Jindal wasn’t the only senior G.O.P. figure who was talking about the need for his party to shed its obsession with protecting the privileges of the wealthy and reach out to middle-class Americans. Marco Rubio, the Florida senator who could well face off against Jindal in the 2016 primaries, said much the same thing, and so did Paul Ryan, Romney’s running mate. “We must speak to the aspirations and anxieties of every American,” Ryan told a Republican dinner. And David Brooks, the Times op-ed columnist, wrote of a “Republican glasnost.”

Flash forward a few weeks, and such statements seem comical. Let’s set aside, for the moment, the dogged rejection by prominent congressional Republicans of calls for stricter gun laws in the wake of the Newtown massacre. In the House of Representatives today, Speaker John Boehner is set to push through a vote on a G.O.P. tax and spending proposal that is a spit in the eye to low- and middle-income Americans and a shameful giveaway to the party’s richest supporters.

The central element of Boehner’s so-called “Plan B” is a proposal to raise the income threshold at which a higher rate of tax would kick in from four hundred thousand dollars—the figure in President Obama’s latest proposal—to a million dollars. Obviously, that would be a boon to people earning half a million dollars a year, or three quarters of a million dollars a year—people who are very well off by any definition. But that is only part of the story. Let’s talk about those lucky Americans who earn more than a million dollars a year: they number about four hundred thousand, which is roughly 0.3 per cent of the total population of tax filers. Under Plan B, these folks would face a higher tax rate on part of their income—39.5 per cent, compared to the current rate of 35 per cent. Boehner’s proposal would appear to hurt them quite a bit, but that simply isn’t the case. Although they would end up paying a bit more in tax than they do now, they wouldn’t pay nearly as much as they would under Obama’s compromise proposal.

As ever, the devil is in the details. While the tax rates of the 0.3 per cent would go up, they would also be allowed to claim many more deductions than they would under the Obama plan. In addition, they would also get to pay substantially lower rates on capital gains, dividends, and inheritances. Since many of them derive much of their income from these sources, this is a big deal. In short, “the Boehner plan maintains several generous tax cuts for incomes over $1 million.” The quote comes from an an invaluable post by Bob Greenstein, the president of the Center on Budget and Policy Priorities, which takes a clinical look at Plan B and cites freshly produced figures from the non-partisan Tax Policy Center. The upshot of these calculations: relative to the President’s latest offer, which limits the deductions that very high earners can take and increases the tax rates they would pay on investment income, the average member of the 0.3 per cent would gain upwards of fifty thousand dollars a year.

You might think that would be enough of a gift to the ultra-rich, and enough of a slap in the face for one day to Jindal, Rubio, Brooks, and other would-be G.O.P. reformers. But you would be mistaken. To help pay for their largesse, Boehner and his colleagues in the House are proposing a big cut in the incomes of some of America’s poorest families. Under Plan B, the federal government would reduce the payments that low-income working families currently receive under two programs designed to help them: the Earned Income Tax Credit and the Child Tax Credit.

In 2009, at the start of the Obama Administration, these programs were enhanced, and, in 2011, according to Census data that Greenstein cites, the changes helped lift 1.6 million Americans, including six hundred thousand children, out of poverty. Under Plan B, these enhancements would come to an end, resulting in substantial income reductions for the affected families. Greenstein gives the example of a mother with two children who works full time earning the minimum wage of $7.25 an hour. At the moment, she makes $14,500 a year and receives an additional get Child Tax Credit of $1,725. Under Plan B, this credit would be slashed to just $165, meaning her income would be cut by $1,560—or about ten per cent.

So, there you have it. Less than two months after being defeated at least partly because it was viewed as a tool of the rich, the G.O.P. is about to vote through a measure that, even by the standards of trickle-down economics, is shameful sop to those who need help least. Plan B’s only conceivable merit is for use as a bargaining chip in the final days of the negotiations over the fiscal cliff. Almost certainly, that is what Boehner has in mind. But in turning down the White House’s latest offer and opting for this sordid gambit, he hasn’t only derailed efforts to reach an early settlement. He’s made a mockery of the G.O.P.’s nascent efforts to reposition itself as a party for all Americans. Whether it realizes it or not, the party still seems intent on self-destruction.

Photograph by Andrew Harrer/Bloomberg/Getty.