I have no idea who is going to win the Democratic presidential nomination, but lately I've been wondering whether, if it is Barack Obama, he might want to consider keeping Dick Cheney on as his vice president.

The controversy unfortunately obscures the larger point, which should be undeniable: the central role of this backlash in the rise of the modern conservative movement.

The centrality of race — and, in particular, of the switch of Southern whites from overwhelming support of Democrats to overwhelming support of Republicans — is obvious from voting data.

For example, everyone knows that white men have turned away from the Democrats over God, guns, national security and so on. But what everyone knows isn't true once you exclude the South from the picture. As the political scientist Larry Bartels points out, in the 1952 presidential election, 40 percent of non-Southern white men voted Democratic; in 2004, that figure was virtually unchanged, at 39 percent.

More than 40 years have passed since the Voting Rights Act, which Reagan described in 1980 as "humiliating to the South." Yet Southern white voting behavior remains distinctive. Democrats decisively won the popular vote in last year's House elections, but Southern whites voted Republican by almost two to one.

The GOP's own leaders admit that the great Southern white shift was the result of a deliberate political strategy. "Some Republicans gave up on winning the African-American vote, looking the other way or trying to benefit politically from racial polarization." So declared Ken Mehlman, the former chairman of the Republican National Committee, speaking in 2005.

And Ronald Reagan was among the "some" who tried to benefit from racial polarization.

True, he never used explicit racial rhetoric. Neither did Richard Nixon. As Thomas and Mary Edsall put it in their classic 1991 book, "Chain Reaction: The impact of race, rights and taxes on American politics," "Reagan paralleled Nixon's success in constructing a politics and a strategy of governing that attacked policies targeted toward blacks and other minorities without reference to race — a conservative politics that had the effect of polarizing the electorate along racial lines."

Thus, Reagan repeatedly told the bogus story of the Cadillac-driving welfare queen — a gross exaggeration of a minor case of welfare fraud. He never mentioned the woman's race, but he didn't have to.

There are many other examples of Reagan's tacit race-baiting in the historical record. My colleague Bob Herbert described some of these examples in a recent column. Here's one he didn't mention: During the 1976 campaign Reagan often talked about how upset workers must be to see an able-bodied man using food stamps at the grocery store. In the South — but not in the North — the food-stamp user became a "strapping young buck" buying T-bone steaks.

Now, about the Philadelphia story: in December 1979 the Republican national committeeman from Mississippi wrote a letter urging that the party's nominee speak at the Neshoba Country Fair, just outside the town where three civil rights workers had been murdered in 1964. It would, he wrote, help win over "George Wallace inclined voters."

Sure enough, Reagan appeared, and declared his support for states' rights — which everyone took to be a coded declaration of support for segregationist sentiments.

Reagan's defenders protest furiously that he wasn't personally bigoted. So what? We're talking about his political strategy. His personal beliefs are irrelevant.

Why does this history matter now? Because it tells why the vision of a permanent conservative majority, so widely accepted a few years ago, is wrong.

The point is that we have become a more diverse and less racist country over time. The "macaca" incident, in which Sen. George Allen's use of a racial insult led to his election defeat, epitomized the way in which America has changed for the better.

And because conservative ascendancy has depended so crucially on the racial backlash — a close look at voting data shows that religion and "values" issues have been far less important — I believe that the declining power of that backlash changes everything.

Can anti-immigrant rhetoric replace old-fashioned racial politics? No, because it mobilizes the same shrinking pool of whites — and alienates the growing number of Latino voters.

Now, maybe I'm wrong about all of this. But we should be able to discuss the role of race in American politics honestly. We shouldn't avert our gaze because we're unwilling to tarnish Ronald Reagan's image.

© 2007 New York Times News Service