No matter which candidate wins the Republican Party's straw poll in Iowa on Aug. 14, one thing is clear: The domination of the GOP by southern conservatives is facing a serious challenge. Underlying the struggle between the right and the center in the Republican Party is a long-range phenomenon -- the decline of the South and the rise of the Sun Belt.

These two trends converge in the figure of George W. Bush, who combines the entrepreneurial fervor of traditional Republican politics with a newfound GOP appreciation of government. Conservative Republicans complain that Bush-who in terms of both public appeal and fund-raising muscle is already the runaway favorite for the nomination-symbolizes the return of the long-discredited "eastern establishment" wing of the Republican Party. But Bush's sensibilities-shunning ideology for pragmatic problem-solving, downplaying traditional divisions of ethnicity and race and embracing governmental initiatives in "new economy" sectors such as technology and education-are much more in line with the emerging Sun Belt. In the 1970s, Kevin Phillips, Kirkpatrick Sale and other observers of American politics predicted the rise of "the Sun Belt." (Phillips coined the term.) The region included California and the Southwest as well as states on the periphery of the South such as Texas and Florida. Indeed, in the early 1970s such a shift appeared to be well under way. The last two presidents had been the Texan Lyndon Johnson and the Californian Richard Nixon. The emergence of a new Republican majority, based in the Sun Belt suburbs, seemed to be symbolized by the career of John Connally, a Texas Democrat who became a Republican and, for a while, Nixon's heir apparent.

But then, in the mid-1970s, something funny happened. The Sun Belt did not take over Washington, D.C. The South did.

Or, rather, the South took over Washington again. Southern politicians have dominated national politics for two long periods of American history. From the inauguration of Thomas Jefferson until the Civil War, the party dominated by the South had disproportionate influence in federal politics. From the Civil War until the 1930s, national politics was dominated by a Northern-Midwestern coalition, symbolized by a series of presidents from Ohio. In 1932, the South returned to power in Washington, led this time by a Northeastern patrician, Franklin D. Roosevelt. Although the New Deal Democrats were a coalition of southern conservatives and populists, Northern labor and immigrants and prairie progressives, southern Dixiecrats, with safe seats secured by one-party politics and the disfranchisement of blacks, ruled Congress from the 1930s to the 1960s.

The civil rights revolution, instead of weakening the Solid South, ironically gave Southern conservatism a new lease on life. The reason was simple: Between the 1960s and the 1990s, white southerners trickled out of the Democratic Party into the Republican Party. Enough white southerners were undecided that they formed a substantial swing vote, for which both the Democrats and the Republicans competed. The only presidential victories for the Democrats after 1968 came when they appealed to the white southern vote by running center-right southern governors who campaigned as folksy populists: Jimmy Carter and Bill Clinton.

Meanwhile, Richard Nixon's "Southern strategy" succeeded beyond all expectations.

Following the 1994 election, hundreds of white southern Democrats switched to the Republican party. The major leaders of the Republican insurgency in the House and Senate-Gingrich, Lott, Armey, DeLay-were all southern politicians.

The Republicans, who had hoped to capture a few southerners, were instead captured by southerners.

But it now appears that the revival of southern domination of national politics between Jimmy Carter and Bill Clinton was ephemeral. For a generation, the South has been influential not because it was solid but because it was divided-because white southerners provided a swing vote. Now that white southerners are the new base of the GOP, neither party has any reason to compete for them. The Republicans can take them for granted, and the Democrats can write them off. The religious right-which, with few exceptions, is the southern right in disguise-has learned to its cost that people stop flirting with you when you are married.

Latinos have replaced white southerners as the most important group of swing voters in American politics. Unlike blacks, who are overwhelmingly Democratic, and white southerners, who are now overwhelmingly Republican, Latinos in Texas and Florida, if not in California, are not committed as a group to either party.

Because Latinos are concentrated in California, Texas, Florida and a few other states, the competition for their vote means that the rise of the Sun Belt -- arrested since the 1970s -- has begun once again. Those who predicted the Sun Belt era in the 1970s believed that its ascendancy would be caused by its economic power, fed by immigration of affluent whites from the North. Instead, the key factor is politics, not economics, and the important immigration is that of working-class people from Mexico and Central America. Nevertheless, the result will be the same: the eclipse of the South by the Southwest (and Florida) as the battleground between the Republicans, with their new base in the South, and the Democrats, with their new base in the Northeast.

American politics in the age of the Sun Belt will differ in its themes and tone from the national politics of the era of southern domination that has just ended. From the 1970s until the 1990s, national politics was shaped-some would say disfigured-by the classic themes of southern politics: demagogic populism and culture war (including thinly disguised racism). Neither southern-style populism nor southern-style culture war will work in the Sun Belt. The Sun Belt, divided among a number of ethnic and racial groups-Anglo, Latino, black, Asian-is less like the biracial South than like the multi-ethnic Northeast. In Los Angeles, as in Chicago or New York City, simplistic appeals to "the people" don't work: Which people do you mean? Successful Sun Belt politicians, like successful Northeastern and Midwestern politicians, must be able to build cross-ethnic coalitions. Parties that pander to one ethnic group, as the Republicans pandered to Anglo nativists in California, will suffer defeat at the polls.

Conservative values appeal to many Sun Belt Americans-Latinos and Asians, as well as whites. But Sun Belt conservatives will be less likely than southern conservatives to launch moral crusades. For many southern politicians from lily-white, all-Protestant towns or neighborhoods, there is a natural equation between being Baptist or Methodist and being American. No such equation has existed in the Northeast and Midwest since the migration of great numbers of German and Irish Catholics in the mid-19th Century; and no such equation will exist in the 21st-Century Southwest.

Sun Belt politics will be more secular than southern politics, not because individual Sun Belters are less religious, but because the region is so diverse that different religious groups will agree on a high degree of public neutrality in order to achieve mutual disarmament in the culture wars.

Perhaps the greatest change will be an intangible one -- from the pessimism of southern politics to the optimism of Sun Belt politics. The history of the American Sun Belt is as stained by brutal racism and vicious class exploitation as that of the South. But the frontier myth of the West is a myth of progress that inspires optimistic politicians as different as Ronald Reagan and LBJ, whereas the South's obsession with the Civil War and slavery produces haunted liberals and vengeful conservatives. What is more, because of the frontier legacy, the formerly Wild West tends to be associated with over-the-top hedonism-California beaches, Las Vegas casinos, Texan spending sprees, Miami vice. The Sun Belt is, among other things, the Fun Belt. An America dominated by the Hispanic borderlands may not be more just, but it will be more cheerful.

The Indian summer of southern dominance in national politics, then, is drawing to a close. To the southern right that has loomed so large in recent years, moderate Sun Belt Republicans-as well as liberals in all regions-can say goodbye. Or rather: Hasta la vista, Bubba.