THE POWER STRUCTURE of the Republican Party in the South, once a sparse network of affluent ideologues committed to the agenda of hardline conservatives like Barry Goldwater, has been transformed into the political home of an ascendant middle class, uniformed in blue blazers and button-down shirts.

This transformation has produced a party elite leaning strongly toward George Bush, the candidate rejected by the South just seven years ago as the Republican presidential candidate most clearly associated with the eastern establishment wing of the GOP.

The alteration of the southern GOP goes far beyond the political preferences for one candidate over another. A generation ago the southern party leadership was the advance guard of a conservative revolution that overthrew the Wall Street wing of the GOP.

The new southern Republican Party is based on the explosive growth of an urban-based middle class that scarcely existed before the 1960s. The party also includes former Democrats who left their party as blacks gained power in the wake of the civil rights movement.

The South, as the dominant partner in an alliance with western mountain states, was the driving force behind the nomination of Goldwater in 1964. And it was the South where the flame for Ronald Reagan burned bright enough through 1976, when he suffered repeated primary defeats in the North, to propel him to victory in 1980.

This year, however, the presidential campaign of George Bush is demonstrating how soon victorious revolutionaries can be converted into a power elite, and how quickly that elite can accommodate itself to changing demographics. From Florida to Texas, men and women who as recently as eight years ago were determined to crush the GOP eastern old-guard have helped to turn the network of southern party leaders and operatives into a bastion of support for Bush, the Republican presidential candidate most clearly tied to the party's old-line, patrician wing.

Bush has identified himself with the programs and initiatives of the Reagan administration, but his base of support remains heavily dependent on the center and moderate wings of the party. His strategists are convinced that a substantial challenge to his presidential bid could be mounted only from the right, the ideological wing of the party that has flourished in the South in the past.

Over the past two years, however, Bush has moved like Sherman's army through the South -- backed by a war chest expected to reach $7 million this month -- to capture much of the southern membership on the Republican National Committee, a host of elected officials and an impressive array of party operatives. Bush's success reflects both the change in outlook of the southern party leadership and the changing class structure ofthe South. As a result, within the universe of southern Republican activists, Bush has, so far, overwhelmed such challenges from the right by candidates like Rep. Jack Kemp (R-N.Y.) and former Republican senator Paul Laxalt of Nevada.

Bush's southern supporters include such early backers of the Reagan and Goldwater movements as Tommy Thomas of Florida, John Grenier of Alabama, Dan Ross of South Carolina and Lou Kitchin of Georgia. These men may not be major figures to the general public, but they were among the first lieutenants commissioned in the Reagan-conservative movement within the Republican Party, some dating back to the Goldwater campaign of 1964 or the Reagan effort in 1968.

Despite the intense antigovernment credentials that these leaders once displayed, the candidates that they have helped elect to statewide office show an entirely different orientation. From Tennessee to Florida, where Republicans have been elected governor, they have initiated major expansion of government's role in education, highway beautification and industrial development. In Florida, the Republican governor, Bob Martinez, successfully won approval of a major tax increase for Medicaid, road construction, new prisons and education.

In fact, the once-revolutionary Republican Party of the South has, in a number of states, reached the point where it has become the target of a new counterrevolution within the GOP: the mobilization of white fundamentalist and charismatic Christians behind the candidacy of televangelist Marion G. (Pat) Robertson.

In South Carolina, Robertson's forces have severely embarrassed -- and in a number of cases, defeated -- a Republican power structure with numerous ties to the Bush campaign. In Richland County, site of the state's capital, the Republican establishment resorted to arcane party rules never before applied and unpublicized meetings to fend off Christian activists intent on seizing control of the county Republican Party. Throughout the South, the Christian Republican right represents lower middle- and working-class workers who reject the more urbane agenda of affluent "country club" Republicans. The Christian Republican right has a deeper commitment to the now largely forgotten "social agenda" that Republicans talked so much about in the early '80s.

The GOP's treatment of insurgent Christians delighted a beleaguered South Carolina Democratic Party. Don Fowler, a South Carolina member of the Democratic National Committee, said "what is happening to the Christians now is the same thing that happened to blacks 20 years ago" when they sought entry into a white-dominated Democratic Party.

The battles within the Republican presidential nomination process reflect broad political and economic changes in the South -- changes that have already altered the balance of power between the national Democratic and Republican Parties.

Twenty years ago, the Republican Party of the South was concentrated among a small number of the elite upper-middle class. Two decades ago, despite the rupture of the "Solid South" in presidential elections, Democratic hegemony persisted at the state and local level; the urban and suburban middle class itself was a minority, outnumbered by farmers, farm workers, and a non-union working class. The GOP was, in effect, an insurgency often led by intensely conservative, hard-right ideologues among a small segment of the affluent.

The southern Republican Party of the 1980s in some respects grew out of the strongest base of the Democratic Party in 1950s. In the 1950s, according to UCLA political scientist John R. Petrocik, Democratic allegiance among whites was strongest among "upper-status whites," whose nearly 5-to-1 commitment to the Democratic Party hinged on their use of the party to retain control of government.

Before the civil rights movement, this elite retained control of state and local government through a one-party system in which the critical decisions were made in low-turnout Democratic primaries with participation highly skewed in favor of the affluent by the use of literacy tests and poll taxes.

"By the 1980s," according to Petrocik, "the class cleavage had reversed itself," as well-to-do whites led the charge to the GOP.

This change resulted in large part from the adoption of pro-civil-rights positions by the national Democratic Party, the passage of federal legislation that opened southern polling booths to blacks and the subsequent collapse of the conservative coalition in Congress in the 1960s and 1970s.

With blacks participating in Democratic primaries, the contests were no longer so subject to elite control. In addition, the deterioration of conservative Democratic muscle in Congress made the party less attractive to many southern whites, rich and poor.

The more recent shifts in the tenor of the Republican Party in the South -- from radical insurgency to allegiance with the establishment -- reflect one of the most rapid regional economic and social alterations in this century. In a matter of just two generations, the South has abruptly transformed itself from an agrarian-based society to a largely urban and suburban society.

During its ascendency from post-Reconstruction through the mid-1960s, Southern Democracy depended on a "plantation elite {that} could virtually control the political agenda of most southern states . . . . {But}, by 1980, a quantum change had occurred, and the new middle class was 23 times greater than the agrarian middle class," Earl and Merle Black write in their current book, "Politics and Society in the South."

As a result of this economic upheaval in the South, the Republican Party has shifted from an insurgency to an established political movement. Its base -- the urban and suburban middle class -- has expanded at a geometric rate, moving from minority status in the days when Goldwater was nominated, to social dominance in the final years of the Reagan presidency.

In effect, the ideologues of the conservative revolution have been overtaken by a massive expansion of a Republican-leaning white middle class. It is in this political and social setting that Bush -- a politician who claims Texas as his home state, but whose family background and style epitomize the blue blood of New England -- has steadily built up a base of support and endorsements. In a certain sense, Bush -- by dint of his origins and more recent political past -- can be seen as a bridge between two political cultures.

Bush's backing includes key political aides to the governors, or the Republican governors themselves in Florida, Alabama, Oklahoma, Texas and South Carolina. In Texas, Bush forces claim to have three quarters of the Republican members of the legislature and a majority of the state GOP executive committee.

John Buckley, spokesman for the Kemp campaign, has sought to downplay Bush's organizing success -- "we acknowledge that there isn't a country club in the South that George Bush doesn't have an endorsement in" -- but privately and publicly, competitors to Bush all agree that he has a decisive organizing edge in the South at the momemt

This network may or may not pay off on March 8, Super Tuesday primary day, but it does suggest that the Republican Party is a very different animal from what it was a decade ago.

In 1980, for example, Lee Atwater proudly boasted of how he organized the Reagan challenge to the South Carolina establishment in that state's GOP primary, overwhelming both Bush and John Connally, along with such local powerhouses as Sen. Strom Thurmond and former governor Jim Edwards. This year, Atwater is managing the Bush campaign, and in South Carolina he has quietly pushed most of the same GOP establishment into the Bush campaign.

Although not directly related to the presidential fight, the same changing patterns can be seen in North Carolina. In 1976, it was the Congressional Club of Sen. Jesse Helms (R-N.C.) that engineered Reagan's unexpected victory over Gerald Ford. That contest was a key demonstration of Reagan's continued political vitality and proved to be a critical step towards Reagan's successful presidential bid four years later. And it has been the Helms organization that has dominated delegations to GOP presidential conventions.

This year, however, Helms' Congressional Club -- a mainstay of conservative Republicanism in the South -- was crushed by the traditional, moderate wing of the North Carolina GOP, backed Governor Jim Martin (R-N.C.), in a head-on fight for control of the party.

The expansion of the Republican base in the South is likely to be accelerated by a political tactic devised by southern Democrats: the holding of what amounts to a regional southern primary on March 8, 1988.

Designed to revive interest in the Democratic primary among white voters, the unanticipated consequence may well be to expand interest in in the more conservative Republican presidential contest.

"If people choose to vote in the Republican primary," said Alvin From, executive director of the Democratic Leadership Council then "it's going to be harder to get them back {to the Democratic Party} in November."

The major development that could emerge on super Tuesday is white indifference to the Democratic primary. According to Earl Black, a political scientist at the University of South Carolina, "Whites don't give a damn who the Democrats are going to nominate."

Thomas Edsall covers politics for The Washington Post.