"He stood for something, and whether you like it or not, that's very powerful in politics," said Fred Smoller, a political science professor at Brandman University, which is part of Chapman University.
During the primaries Mansoor announced that Costa Mesa would not tolerate illegal immigrants. It isn't a "sanctuary city," he proclaimed, but a "rule of law" city.
He also introduced his own measure in 2005 to have Costa Mesa police officers check the immigration status of suspects, long before Arizona passed Senate Bill 1070.
This hardline stance may have helped him carry Costa Mesa, where he won by a margin of 59% to 41%, according to uncertified results.
Voters chose Mansoor by about the same proportion in the parts of the district other than Westminster and Garden Grove, the two most heavily Vietnamese cities.
Ultimately, he won by 55.8% to 44.2%.
In Westminster and Garden Grove, the candidates split the vote: 50.2% for Nguyen and 49.8% for Mansoor.
Nguyen's strong ties to Little Saigon — he was a key organizer for the Tet Festival and active in other groups — certainly boosted him there.
Nguyen says that based on his polling, four out of five Vietnamese voters chose him.
"It wasn't a challenge. The majority of the Vietnamese community voted for me," he said. "We were confident we got that."
But some say he may not have won over the older generation of active Vietnamese voters, who traditionally vote Republican and are especially conservative.
Mansoor and some within Little Saigon criticized Nguyen for his family's business ties to the Communist government in Hanoi. He is vice president of a remittance company that sends millions of dollars to people in Vietnam each year. The anti-Communist strain in Little Saigon is legendary — many immigrants came during or after the Vietnam War and still harbor resentment.