Mitt Romney’s tax and spending plans are so irresponsible, so cruel, so extreme that they are literally incredible. Voters may find it hard to believe anyone would support such things, so they are likely to discount even factual descriptions as partisan distortion.

The pro-Obama New Priorities PAC stumbled across this phenomena early in 2012 in its focus group testing. When they informed a focus group that Romney supported the budget plan by Rep. Paul Ryan (R-Wis.), and thus championed ending Medicare as we know it while also championing tax cuts for the wealthy, focus group participants simply didn’t believe it. No politician could be so clueless.

Incredulity may complement what New York Times columnist Maureen Dowd dubbed Romney’s strategy of “hiding in plain sight.” Romney refuses to release his tax returns, scrubbed the records and e-mails of his time as governor and as head of the Olympics, keeps secret details of his Bain dealings and covers up the names of his bundlers. And then, he’s able to announce extremely cruel policy positions with impunity, because the voters just can’t believe that’s what he is for.

This is what comes to mind with the publication of a study on the effects of the Romney tax policy by the non-partisan Tax Policy Center and the Brookings Institution.

The study took its assumptions from Romney’s tax agenda on his Web page — where he promises to cut tax rates by 20 percent, sustain all the Bush tax breaks, keep the reduced rate for capital gains, eliminate the Alternative Minimum Tax, eliminate capital gains taxes on married families earning less than $200,000 (or as Gingrich noted, on those that don’t have any capital gains) and eliminate the estate tax (a small boon to his strapping sons).

Romney then promises to make these cuts without losing revenue by eliminating tax loopholes. Only he refuses to identify which tax breaks or loopholes he would eliminate.

Under the best (and most improbable) of circumstances — that the Congress decided to completely eliminate tax expenditures for those making over $200,000 before reducing any of the benefits to those making under that amount — the study found that Romney’s tax plan would transfer a staggering $86 billion in tax burden from those making over $200,000 to those making under that amount. Millionaires would pocket an average tax cut of $87,000 while everyone else would suffer a tax hike of $500 a year.

That’s because to make up for the lost income, Congress would have to cut the mortgage deduction, the deduction for gifts to charity, the deduction for employer based health care, the Earned Income Tax Credit and child tax credit that goes to middle- and lower-income earners. But simply eliminating these and other tax breaks for the rich doesn’t generate enough revenue. So the people who really take it in the teeth are middle-income earners — small business people, middle management and professionals. It is, the study concluded, “not mathematically possible” to lower tax rates as Romney proposes without giving the rich a tax break and working and middle-income people a tax hike.

But will people believe that Romney really is for that — more tax breaks for the rich paid for by tax hikes on working families? Most of course will never learn about the Romney tax plan. But even those that do, could they ever accept the incredible truth?

Last month, the Democracy Corps, led by Stan Greenberg and James Carville, released a survey arguing that Obama and Democrats benefit greatly when the election is framed as a choice on the Republicans’ Ryan plan, the extreme budget passed by the House of Representatives, that exacts deep cuts in education, programs for poor children and turns Medicare into a voucher that pushes more and more costs on seniors.

In their survey, Obama’s margin over Romney “more than doubles” when the election is framed on the two candidates’ position on the Ryan budget. That of course, assumes that the election can be so framed, and that the voters will accept the assumption. But as the Priorities crowd discovered, voters have a hard time believing any politician could be supporting 20 percent cuts in education, an elimination of the refundable tax credit for children or dramatically changing Medicare. That is simply too extreme to be believed.

Ironically, of course, if Romney is elected and Republicans keep the House, the tea party right will claim a mandate. As Grover Norquist says, the House will drive the agenda and Romney will sign anything that emerges from the Senate. And sadly, given that the millionaires on the Democratic side of the Senate aisle aren’t nearly as united as those on the Republican side — and many are dependent on funding from some of the same special interests that now dominate Washington — we’re likely to see less Senate obstruction and more “bipartisan cooperation” on an agenda that Americans consider literally incredible.

The only hope is that voters take another look before they decide to vote for a change. In the case of Romney, the Republican really does support a budget plan that would scrap Medicare and give tax breaks to millionaires. He really is planning to eliminate Wall Street safeguards and take away health-care benefits from millions. He really believes the country will be better off if more teachers and police officers are laid off and foreclosures continue unabated.He really does want to deregulate Wall Street again, and gut the protections the EPA provides for clean air and clean water, to say nothing of global warming, the existence of which he now denies.

This isn’t a liberal caricature based on election-year demagoguery; this is Mitt Romney’s policy agenda. That is truly incredible — incredibly true.