LAT:

The upset marked a political earthquake in central Orange County, an ethnically diverse area dominated by Latinos in Santa Ana and Asian Americans in the Little Saigon area. It’s the only part of Orange County where Democrats hold a voter registration advantage over Republicans.

But a Los Angeles Times analysis of election results shows how Republicans can still win because Asian American voter turnout is so much higher than Latino turnout.

The outcome, the analysis found, turned on the high number of Santa Ana voters who failed to return the absentee ballots that had been mailed to them.

In the core of Santa Ana, where voting heavily favored Correa, only 22% of the absentee voters got around to returning their ballots, far below the state and county’s 50% return rate for absentee ballots in the 2014 general election. The unreturned ballots represented tens of thousands of votes.

Andrew Do, by contrast, got a big boost because more than 40% of the absentee voters in Little Saigon returned their ballots.