SANTA ANA, Calif. – Orange County has been a national symbol of conservatism for more than 50 years: birthplace of President Richard M. Nixon and home to John Wayne, a bastion for the John Birch Society, a land of orange groves and affluence, the region of California where Republican presidential candidates could always count on a friendly audience.

But this iconic county of 3.1 million people passed something of a milestone in June. The percentage of registered Republican voters dropped to 43 percent, the lowest level in 70 years.

It was the latest sign of the demographic, ethnic and political changes that are transforming the county and challenging long-held views of a region whose colorful – its detractors might suggest zany – reputation extends well beyond the borders of this state.

At the end of 2009, nearly 45 percent of the county’s residents spoke a language other than English at home, according to county officials. Whites now make up only 45 percent of the population; this county is teeming with Hispanics, as well as Vietnamese, Korean and Chinese families. Its percentage of foreign-born residents jumped to 30 percent in 2008 from 6 percent in 1970, and visits to some of its corners can feel like a trip to a foreign land.

The demographic changes that have swept the county reflect what is happening across the state and much of the nation. It has happened slowly but surely over the course of a generation, becoming increasingly apparent not only in a drive through the 34 cities that fill this sprawling 789-square-mile county south of Los Angeles, but also, most recently, in the results of a presidential election. In 2008, President Barack Obama drew 48 percent of the vote here against Sen. John McCain of Arizona. (By comparison, in 1980, Jimmy Carter received just 23 percent against Ronald Reagan, the conservative hero whose election as California governor in 1966 and 1970 was boosted in no small part by the affection for him here.)

"I was a city planner in San Diego in 1960 when Orange County was just orange groves and typecast as a conservative stronghold," said Marshall Kaplan, the executive director of the Merage Foundations, which runs educational and other programs for recent immigrants here. "It isn’t anymore. I live in Irvine. My wife is Asian. In Irvine, I sometimes feel like I’m her affirmative action program."

Manuel Gomez, the vice chancellor of student affairs at the University of California, Irvine, said the county where he was born 63 years ago is almost unrecognizable to him today. "With diversity comes more cultural voices and political voices," he said. "And certainly better food."

Orange County is not unique in being a reliable Republican region in California. But this county has always boasted of a zesty political brand: almost defiantly conservative, the anti-Los Angeles, a land of gated communities and great wealth that managed to produce a steady stream of colorful conservative figures, including the televangelist Robert H. Schuller and former Rep. Robert K. Dornan – B-1 Bob, as he was known, for his advocacy of military projects. (In a sign of what was to come, Dornan lost the House seat in 1996 to a Democratic Latina, Loretta Sanchez).

With such world-famous attractions as Disneyland and Schuller’s Crystal Cathedral and enclaves like Laguna Beach and Balboa Island, Orange County is as much a symbol in California as it is nationally.

Indeed, to some measure, the extent of the county’s transformation may seem magnified simply because of the way people thought of it in the past. "The new Orange County is not a repudiation of the old," said Kevin Starr, a California historian. "For all the attention paid the right-wingers there, they never really took up the whole place. They were just more mediagenic than everyone else."

Still, by any measure, this is no longer Nixon’s Orange County.

Here in Santa Ana, a sign on a downtown furniture store the other day advertised a sale in Spanish only; nearly 95 percent of the enrollment in the public schools is Latino. The mayor of Irvine, Sukhee Kang, was born in Korea, making him the first Korean-American to run a major American city. "We have 35 languages spoken in our city," Kang said.

A few miles away in Westminster – where Vietnamese immigrants began arriving nearly 30 years ago, earning the area the name Little Saigon – is a dazzling sea of Vietnamese characters on storefronts and billboards (including one for McDonald’s). "I’ve been here for 30 years," said Kinh Tram, 59, as he sat in front of a two-story mall that was crowded with other Vietnamese immigrants. "When I first came here, most of these were open lots."

There are pockets of deep poverty spread across a county long identified with suburban affluence and escape from urban Los Angeles. About 25 percent of residents here did not have health insurance at some point during 2009, according to a report released last week by the UCLA Center for Health Policy Research. Less than a mile from the entrance to Disneyland is a Latino enclave of low-income housing where trucks arrive every morning, with names like Yucatan Produce, to sell groceries and household goods to people who cannot afford a car to drive to the store.

Orange remains a Republican county, at least relatively: an influx of immigrants certainly does not equate to automatic Democratic gains, here or anywhere else across the country. Many Vietnamese immigrants are socially conservative and run for office as Republicans. Until the increased identification of the Republican Party with tough measures on immigration in recent years, Latino voters were also clearly in play for Republicans. Most elected officials in Orange County are Republicans.

But the political texture of this county, which is larger in population than Nevada or Iowa, is changing, and many officials say it is only a matter of time before many Republican officeholders get swept out with the tide.

While Republicans have been on a steady decline – in 1990, they made up 56 percent of the electorate – the percentage of independent voters, as in much of the state, soared to 20 percent this past June from 8.6 percent in 1990. Obama’s strong showing here in 2008 continued a nearly 30-year pattern in which the vote for Democratic presidential candidates has steadily increased.

Tram, the Vietnamese immigrant in Westminster, said that he had voted for Obama and that he thought most of his Vietnamese friends had done the same. "The Republicans are for rich people," he said.

A large reason for this transformation is immigration. But the changes also reflect how the regional economy has changed, with the shrinking of the aerospace industry, which supported the once dominant, mostly white middle-class community here. That has largely been taken over by service, tourism and high-tech jobs, the result being that this county is a contrast of the extremely wealthy and the lower middle class.

"It’s less of a middle-class suburb today," said Michael M. Ruane, the director of the Orange County Community Indicators Project, which studies economic and demographic trends in the county. "You have areas of poverty and areas of great affluence and less of a middle."

Even fans of the recent hit television series "The O.C.," whose main characters were prosperous white residents of Newport Beach, got little hint of the diversity of the region. "The county is becoming more like California," Ruane said. "The national image that it is an entirely conservative and entirely Republican county is wrong. Voter registration patterns and voting have shifted as a result of these demographic shifts."

© 2010 The New York Times Company