When you hear about the low, low taxes of people like Mr. Romney, what you need to know is that it wasn’t always thus — and the days when the superrich paid much higher taxes weren’t that long ago. Back in 1986, Ronald Reagan — yes, Ronald Reagan — signed a tax reform equalizing top rates on earned income and capital gains at 28 percent. The rate rose further, to more than 29 percent, during Bill Clinton’s first term.

Low capital gains taxes date only from 1997, when Mr. Clinton struck a deal with Republicans in Congress in which he cut taxes on the rich in return for creation of the Children’s Health Insurance Program. And today’s ultralow rates — the lowest since the days of Herbert Hoover — date only from 2003, when former President George W. Bush rammed both a tax cut on capital gains and a tax cut on dividends through Congress, something he achieved by exploiting the illusion of triumph in Iraq.

Correspondingly, the low-tax status of the very rich is also a recent development. During Mr. Clinton’s first term, the top 400 taxpayers paid close to 30 percent of their income in federal taxes, and even after his tax deal they paid substantially more than they have since the 2003 cut.

So is it essential that the rich receive such a big tax break? There is a theoretical case for according special treatment to capital gains, but there are also theoretical and practical arguments against such special treatment. In particular, the huge gap between taxes on earned income and taxes on unearned income creates a perverse incentive to arrange one’s affairs so as to make income appear in the “right” category.

And the economic record certainly doesn’t support the notion that superlow taxes on the superrich are the key to prosperity. During that first Clinton term, when the very rich paid much higher taxes than they do now, the economy added 11.5 million jobs, dwarfing anything achieved even during the good years of the Bush administration.

So Mr. Romney’s tax dance is doing us all a service by highlighting the unwise, unjust and expensive favors being showered on the upper-upper class. At a time when all the self-proclaimed serious people are telling us that the poor and the middle class must suffer in the name of fiscal probity, such low taxes on the very rich are indefensible.