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 [Democrat Lou] 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.
[Republican] Andrew Do, by contrast, got a big boost because more than 40% of the absentee voters in Little Saigon returned their ballots.
The special election swung nearly entirely on mail-in ballots, which made up about 84% of the total vote.