The claim that 90 percent "saw their incomes decline" came from a New York Times article about a study of the top 10 percent of income tax returns by Thomas Piketty and Emmanuel Saez. Those economists never claimed to have examined incomes of the bottom 90 percent because that cannot possibly be done by looking only at income reported on tax returns. As they acknowledged in The American Economic Review last May: "Our database also suffers from important limitations. In particular, our long-run series are generally con?ned to top income and wealth shares and contain little information about bottom segments of the distribution."

Clinton considers herself "a thoroughly optimistic and modern progressive." Optimistic progressives and liberals find her old-fashioned and grumpy.

The day after Clinton's speech, Washington Post columnist Steven Pearlstein wrote, "To hear it from Democratic leaders and presidential candidates, you'd think the American dream was melting away as quickly as the glacial ice floes in Greenland." He called attention to a Progressive Policy Institute report by Stephen Rose about "The Trouble With Class-Interest Populism."

The class-interest paper from Pew and Brookings asserts that median family income should keep pace with worker productivity, for example, which might make sense if all income came from work and everyone worked. Rose, by contrast, observes that median income includes a growing fraction of seniors and young singles and students. Excluding those under 29 and over 60 lifts median income from about $44,500 to $63,000.

Defining middle class as a real income between $30,000 and $90,000, Rose finds that group did indeed shrink from 47 percent to 37 percent of all households between 1979 and 2004. But that was only because the percentage earning more than $90,000 increased from 29 percent to 38 percent. Rose warns against presidential campaigns based on pitting labor against business or blue-collar against white-collar, because "the group that could reasonably be categorized as having a clear, class-based interest in voting for Democratic policies would comprise less than one-quarter of the population."

Not all Democrats seeking the highest office have yet succumbed to the divisive and hypocritical "Two Americas" theme that quickly made the affluent Sen. Edwards such an implausible candidate. Yet Hillary Clinton just jumped into that trap. Presidential candidates with the highest name recognition have the most to lose by misjudging the electorate.

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Note: This is my last regularly syndicated column, but I certainly do not intend to stop writing. Recent and future work can be found under my bio at cato.org, and several older writings are archived under "policy bot" at heartland.org.