-- Ever since Ronald Reagan became president, the Democrats have had a challenge: They've needed to reinvent populism.

Under Reagan, and now far more so under George W. Bush, the official policy of the U.S. government has been to throw money at the rich. When Reagan ruled, this policy was justified by the doctrine of trickle-down economics: The rich would invest their tax cuts in job-creating American enterprises. The theory sounded a lot better than the actual process worked, but at least there was a theory. Under the latter Bush, there's not even that. When the rich invest today, their money flows to enterprises that span the globe. Trickle-down economics is gone; what we have today is trickle-out economics.

That's only one reason why a rising tide no longer lifts all boats. Throw in the decline of unions and what you get -- and what we have today -- is not a jobless recovery but a raise-less one. With wages stagnating, health care costs rising and college tuition soaring, this should be a moment, if not an era, of Democratic populism.

And it is -- sort of. During the primary season, John Kerry spoke of Benedict Arnold corporations and John Edwards told the tale of the "two Americas" to great effect. But the Democrats go into the general election, as they have in the past several elections, needing to woo two distinct swing constituencies with two distinct takes on the traditional populist message. The downscaled and outsourced industrial workers whom the Republicans have courted by exploiting the politics of cultural traditionalism are receptive to a full-throated populism. The more upscale swing voters may be repelled by Bush's exploitation of such concocted issues as gay marriage, they but can be made uneasy by latter-day Huey Longs taking out after economic elites.

The Democrats' challenge this year is not only to speak to both constituencies but also to claim the mantle of the national unity party. The polling makes clear that Americans understand that Bush has governed from the right and for the rich. No American president since Richard Nixon has so fundamentally relied on manipulating cultural divisions to politically sustain his administration. All that has left the field wide open for John Kerry to pitch to McCain Republicans, to pledge to govern in a more inclusive and even bipartisan fashion. But how do you preach unity and populism -- both necessary and valid elements of any successful Democratic campaign this year -- at the same time, in the same speech?

If anyone has a momentary feeling that this can't be done, may I gently refer you to Bill Clinton's speech on the opening night of the convention, which I suspect will be studied as the seminal statement of reinvented populism. Building on themes of his own presidency and on John Edwards's "two Americas" speech, Clinton created a populism without heavies, a populism whose anger is directed not at economic elites but at George W. Bush for shortchanging agreed-upon national needs by pampering those elites with tax cuts.

Picking up the cudgel of class warfare that Bush has compelled the Democrats to fight, yet making clear he was not targeting upscale voters as the villains, required Clinton to choose as his representative Bush-beneficiary a guy he thought rather highly of. In an indication that he's lost none of his political cunning, Clinton chose himself.

"I almost sent them a thank-you note for my tax cuts," Clinton said, "until I realized the rest of you were paying the bill for it." And then he was off on a Clintonian riff demonstrating yet again that he is the Democrats' greatest framer of issues since Franklin Roosevelt. "They chose to protect my tax cut," he said again and again, over after-school programs and cops on the street and port security. Bush and the Republican leaders in the House "thought our $5,000 [in tax cuts to wealthy families] was more important than doubling the container checks at our ports and airports."

That's not just universalistic populism. It's national security populism. It's a mantra for Democratic victory.

Indeed, the first night of the Democratic convention was close to pitch-perfect. The attacks on Bush were less frontal than inferential and comparative, and more effective for that. ("Strength and wisdom are not opposing values," Clinton said to perhaps the loudest cheer of the night.) Kerry's credentials for becoming commander in chief were loudly sung; Bush's record as commander in chief was loudly impugned -- in part because he subordinates even security to tending his well-frocked flock.

As the Democrats paint it, Bush's favoritism toward the rich imperils us all. A winning populism for our rightly nervous time.