Many of the touchstones of Orange County’s storied conservatism — the birthplace (and resting place) of Richard M. Nixon, the incubator of the right-wing John Birch Society, the political base of Ronald Reagan — are now decades out of date. The county has steadily transformed into one of the nation’s premier electoral battlegrounds, a place where political and demographic cross currents are all colliding.

Nestled along the scenic coastline south of Los Angeles, Orange County has seen an influx of Asian and Latino residents and a backlash from some white voters resistant to change. The college-educated and affluent white voters who once were the backbone of Orange County Republicanism have increasingly turned away from the G.O.P. in the Trump era.

The old Orange County represented the cutting edge of Republican politics. Now, in many ways, the county represents the new face of America, and its divisions…

Today, more than one in three of the county’s residents are Hispanic and more than one in five are Asian, according to census data. Forty-five percent of residents speak a language other than English at home. In Santa Ana, 96 percent of the 45,000 students in the school district are Latino. Not far away is Little Saigon, home to the densest population of Vietnamese Americans in the nation. The two Republicans who won back House seats in 2020, Michelle Steel and Young Kim, are both Asian American women.