In a demonstration of how rapid growth is changing the political landscape of the Sun Belt, Phoenix voters Wednesday threw out a system of city government that has existed since the early days of the century in favor of one that they hope will provide more responsive representation.

By 51 to 49 percent, Phoenix voters in a special election said they preferred an eight-member city council elected by geographic districts over the existing six-member council elected at-large, or citywide.

The Phoenix vote is the latest, and perhaps most significant, example of how migration and population growth in the Southwest and West are bringing about new coalitions of political power. That happened in Houston a year ago, when Kathy Whitmire drew a strong vote from the city's new residents to become the first woman mayor in the city's history.

At-large systems of city government have fallen in other cities in the Sun Belt in recent years. In many cases, the at-large systems had been used to frustrate the aspirations of black and Hispanic voters, and some were challenged under the Voting Rights Act. That occurred in San Antonio in 1977, and the district system that emerged contributed to the election of Henry Cisneros last year as the city's first Hispanic mayor since the early days of the Texas Republic.

In Phoenix, however, the energy behind the movement to create a district system came not from the Hispanic community, which makes up about 15 percent of the population, but from residents in many of the newer neighborhoods who felt that city hall was dominated by a self-appointed business elite that overlooked their needs.

"It was people sick and tired, filled to the gills, with the city government," said Terry Goddard, 35, a lawyer and son of a former Arizona governor who led the petition drive that put Proposition 200, as it was called, on the ballot. "They don't want city fathers telling them what to do."

The special election was held after Goddard and others forced the proposition to a vote by collecting 17,000 signatures on petitions last summer. Proposition 200 was opposed by Phoenix Mayor Margaret Hance, five of six members of the city council and, more importantly, the business and corporate power structure that has ruled Phoenix politics since the end of World War II.

Goddard refused to characterize the vote as old Phoenix versus new Phoenix, saying his proposal earned support throughout the city. But from the way the issue was drawn in the campaign leading to Wednesday's vote, it was clear this was a struggle between those who have dominated the city and those who felt left out of the process, especially residents of some neighborhoods who were angered over two freeways proposed by the council.

The opponents of Proposition 200 spent around $150,000 trying to defeat the measure, warning that it would bring "Chicago-style" ward politics to Phoenix. That opposition included the two city papers, the major banks and other large corporations, as well as the Phoenix 40, a business leadership group.

They did everything they could to defeat the measure, naming it after a ballot initiative that was soundly defeated in November, scheduling the election on a Wednesday and moving some of the polling places from their Nov. 2 locations.

But Goddard's Committee for District Representation countered with an effective television ad campaign attacking those organizations for the way they have controlled city government, and appealing to the nation's "200-year history" of district representation.

Mayor Hance said she was "disappointed" by the outcome, adding, "This is not a mandate. But the voters have sent us a message that they want a change in how they elect their city officials."

Hance, in the face of an earlier petition drive to institute a partial district system, had appointed a task force to recommend changes in the structure of the city government. The future of that committee is not clear.

Special correspondent Don Harris contributed to this report.