Mr. McCain wants to preserve almost all the Bush tax cuts, and add to them by cutting taxes on corporations. Mr. Obama wants to roll back the high-end Bush tax cuts — the cuts in tax rates on the top two income brackets and the cuts in tax rates on income from dividends and capital gains — and use some of that money to reduce taxes lower down the scale.

According to estimates prepared by the nonpartisan Tax Policy Center, those Obama tax increases would fall overwhelmingly on people with incomes of more than $200,000 a year. Are such people rich? Well, maybe not: some of those Mr. Obama proposes taxing are only denizens of lower Richistan, although the really big tax increases would fall on upper Richistan. But one thing’s for sure: Mr. Obama isn’t planning to raise taxes on the middle class, by any reasonable definition — even that of the Bush administration.

O.K., the Bush administration hasn’t actually offered a definition of “middle class.” But in May, the Treasury Department — which used to do serious tax studies, but these days just churns out Bush administration propaganda — released a report purporting to show, by looking at the tax bills of four hypothetical families, how the middle and working class would be hurt if the Bush tax cuts aren’t made permanent.

And when the Center on Budget and Policy Priorities looked at the report, it made an interesting catch. It turns out that Treasury’s hypothetical families got all their gains from the so-called middle-class provisions of the Bush tax cuts: the Child Tax Credit, the reduced tax bracket for lower incomes and marriage penalty relief.

These all happen to be provisions that Mr. Obama proposes leaving in place. In other words, the Bush administration itself implicitly defines the middle class as consisting of people making too little to end up paying additional taxes under the Obama plan.

Of course, all the evidence in the world won’t stop Republicans from claiming, as they always do, that Democrats are going to impose a crippling tax burden on ordinary hard-working Americans. But it just ain’t so.