It was the home of Richard Nixon, the cradle of Ronald Reagan's career and, for decades, a virtual synonym for the Republican Party of California.
Now, for the first time since the Great Depression, Orange County is on the verge of choosing a Democrat for president, which would end the longest streak of Republican presidential victories of any county in the state.
That possibility symbolizes how the American political map has been upended by Donald Trump. He has sped up a decade-long shift in which the GOP has gathered strength in white, blue-collar regions that once routinely elected Democrats, but traditional Republican suburbs increasingly have abandoned the party.
In such counties as Chester in Pennsylvania, Gwinnett in Georgia and Tarrant in Texas, big, affluent suburbs seem likely to shift significantly toward Hillary Clinton this week, according to analysts who track county-level voting trends.
That's an immediate problem for the Republican Party, which has long counted on suburban strength to offset Democratic votes in the cities. It could be an even bigger problem in the long term because those suburbs are among the nation's most economically dynamic, growing regions.
The shift reflects changing demographics: As with Orange County, many of the nation's suburbs have become racially and ethnically diverse, shedding their status as all-white enclaves.
It has been accelerated by Trump's weakness among college-educated, white voters. That group has sided with the Republican in every presidential election since reliable polling began in the U.S. in the 1940s, but this year it has consistently shown a Democratic majority in polls.
Because of the demographic changes, "the question is not whether or not a Democrat is going to win in Orange County, it's just a question of when," said Jon Fleischman, a conservative blogger who lives in Anaheim Hills.
"If Donald Trump were not at the top of the ticket, I don't think it would be this year," he said. "Because he is, it may very well be the case."
Cynthia Ward, 50, a historical preservationist and longtime GOP activist from Anaheim, expressed the sort of dismay that has caused many Orange County Republicans to consider abandoning their party's ticket.
Ward said she could never cast a ballot for Clinton but does not know if she can vote for Trump.
"He's so verbally offensive to so many people that it's distasteful to have someone like that as the standard bearer of the party," she said.
"It has never occurred to me to not vote the Republican ticket," she said. This time, however, she said she may write in a candidate, vote for a third party or just leave the presidential line on her ballot blank.
"This is a bad year," she said. This is a really rough year."
Orange County's ties to the conservative movement stem from its orange-grove roots. Its agricultural heritage meant the county had an anti-union mindset long before its acres of citrus trees gave way to tidy tracts of suburban homes in meticulously planned _ and often gated _ communities.
As the county grew, its conservatism gained reinforcements. White families fled here from an increasingly diverse Los Angeles, especially after the Watts riots in 1965. Conservative transplants from the Midwest also arrived in large numbers.
Conservative religious leaders broadcast sermons from Orange County pulpits across the nation, creating national profiles for Robert Schuller from the Crystal Cathedral and Paul Crouch of the Trinity Broadcasting Network.
The county also developed a hawkish bent as it became home to men who served at the region's military bases or worked in the once-burgeoning aerospace and defense industries.
Daniel Erinton, an electrical engineer who worked at a now-closed Hughes facility in Fullerton, blames former President Bill Clinton for the defense industry's decline.
"He killed it, he just killed it," said the Republican who plans to vote for Trump. "With Hillary, we're going to get more of the same. I think America needs to be strong. We need to show our strength. Peace through strength _ I think Donald Trump will do that again."
Along with conservative voters, the county was a huge source of money for the Republican Party. Wealthy business-minded conservatives like Donald Bren, William Lyon and George Argyros, opened their mansions and their Rolodexes to Republican candidates, making the county a must-stop for politicians.
"All of that became the DNA of the community," said Fred Smoller, a political science professor at Chapman University in Orange. "That's all changing."
In 1990, nearly two-thirds of the county's population was white. Now, they are a minority. The county's Latino and Asian populations have grown enormously _ some in low-income neighborhoods, particularly in Santa Ana, but many in newly diverse, affluent communities.
As the region has grown more diverse, Republican majorities margins have shrunk.. The last time a Democrat took Orange County was 1936, when Franklin Delano Roosevelt won by nearly 12 percentage points. In 1980 and 1984, Ronald Reagan won by 50 points. But in 2008, Barack Obama came close to flipping the county, losing by 2.5 points to Sen. John McCain.
Trump's disparaging rhetoric about Mexicans and Muslims, his breaks with past Republican stands on trade and the overall tone of his campaign seem likely to create the final tipping point this month.
"He's a bad fit for upscale suburbs," said Stu Rothenberg, a veteran nonpartisan political analyst. "They expect a certain style from their presidential nominee, a certain intellect and a kind of measure in serious discussion of policy."
The GOP's problem is most acute among college-educated white women.
"Trump is a bully and a misogynist and incompetent," said Anna Hornbostel of Mission Viejo.
The Republican, who holds a master's in education and is studying for a second one in marriage and family therapy, is no fan of Hillary Clinton. "She's a career politician, and I think she embodies everything that's wrong with the system," she said.
But Trump has her considering a Democrat for the first time in her life. His language about women appalls her, she said.
"I'll probably end up voting for Hillary _ closing my eyes and plugging my nose _ because I trust her ability as a politician to not ... get us into a nuclear war," she said.
Local Democrats also hope that Clinton's coattails and an expected drop in Republican turnout will help them win congressional, legislative and local races.
U.S. Rep. Darrell Issa, whose district includes part of southern Orange County, is the most prominent Republican elected official in the region who may be at risk this year, but other races farther down the ballot could also be affected.
Nelida Mendoza Yanez said Trump is helping Democrats' efforts. Born in Jalisco, Mexico, she has lived in Santa Ana since her parents moved here in 1965, served as a sergeant in the Army and is now a community college board member.
Minorities in Orange County have failed to turn out to vote, undermining their strength, Yanez said as she canvassed for Michele Martinez, a Latina Democrat running for the county Board of Supervisors.
The 1st District _ home to the county's most populous and diverse cities _ is evidence of that. Over the past four decades, it has been represented by a Democrat for just two years.
"That has been the mindset in the past: 'Why vote because they're going to do whatever they want anyway,'" Yanez said. "We're changing that mindset. We're going to make (Orange County) blue!"
