This post is part of Mischiefs of Faction , an independent political science blog featuring reflections on the party system.

Asian Americans tend to be treated as a monolithic bloc in political coverage. We know, for example, that Asian Americans preferred Hillary Clinton to Donald Trump by a 65-27 percent margin last year. But that obscures some important variation within the Asian-American community, which became clearer thanks to a recent and unusual Asian-Democrat-versus-Asian-Democrat congressional race. The results show divergent voting patterns across Chinese-American, Indian-American, and Vietnamese-American voters.

The top two open primary system, adopted by California voters in 2010, allows two candidates from the same party to advance from a primary contest to the general election. In 2016, longtime Democratic US Rep. Mike Honda of San Jose faced Democratic challenger Ro Khanna in the general election, creating a situation in which two Asian Americans from different countries of origin (Honda is Japanese American and Khanna is Indian American) and from the same party vied for California’s 17th congressional district, the one Asian-American-majority district in the mainland US.

According to the American Community Survey’s 2015 estimates, Asian Americans account for 52.9 percent of the congressional district’s total population. The number of Chinese voters (34,055) alone in 2016 was nearly equivalent to the number of Latino voters (34,538) in the district. Consistent with prior research, decline to state registration numbers is relatively high among Asian-American voters. Notably, in the 2016 general election more decline to state Asian Americans turned out than either Asian American registered Democrats or Republicans.

Table 1: party ID of voters in 2016 general election by race/ethnicity, California congressional district 17

Using ecological inference techniques, we can estimate the proportion of these racial subgroups that voted for the candidates. To conduct the analysis, I use precinct-level voter returns with voter registration data and surname matching to identify voters based on their race and ethnicity.

Using Rosen et al.’s (2001) rows by columns method of ecological inference, I paint a picture of how Honda garnered a coalition of support in 2012 and 2014, but failed to do so in 2016. In 2012, Honda won reelection handedly against Chinese-American Republican challenger Evelyn Li. The district, which voted strongly in favor of Obama, lent its support to incumbent Democrat Honda. With two Democrats on the general election ballot in 2014, both of Asian-American heritage, voters were offered a different set of options.

The estimations suggest that Honda’s win in 2014 was heavily reliant upon Latino support, while Asian Americans and voters of other races and ethnicities began to shift their support toward Khanna. Two years later and amid allegations of ethics violations, Honda continued to receive strong support from Latino voters in the district, but a coalition of Asian-American and other voters moved heavily toward Khanna, propelled by a larger presidential year turnout.

Table 2: estimated support for candidates by race or ethnicity, CD 17 2012-16

(Standard errors appear in parentheses)

Disaggregation of Asian-American voters by country of origin suggests that Chinese Americans and Indian Americans in particular voted heavily in favor of Khanna in 2016. An estimated 81.2 percent of Chinese-American voters and 89.82 percent of Indian-American voters in the district lent their support to Khanna in 2016, while Honda garnered an estimated 70.41 percent of Vietnamese Americans’ support.

Table 3: estimated support for candidates by Asian race/country of origin, CD 17 2012, ’16

(Standard errors appear in parentheses)

These results raise the question: Why did Indian- and Chinese-American voters move to support Khanna while Vietnamese Americans maintained their allegiance to Honda? One contributing factor could be negative ads run by the Honda campaign that were accused of evoking prejudice of Indian Americans. A group of Silicon Valley Indian Americans responded to the ad with an open letter criticizing Honda for a lack of tolerance and acceptance. The sentiment may have had a spillover effect to Chinese Americans in the district, many of whom also work in Silicon Valley. Khanna’s campaign received significant support from tech moguls like Google CEO Sundar Pichai and Facebook COO Sheryl Sandberg.

Vietnamese voters have been found in prior research to lean toward the Republican Party. In California’s 17th congressional district, however, Vietnamese Americans appear to have lent consistent support to Honda in 2012 and 2016. Honda, a Japanese American who was sent to an internment camp as a young boy during World War II, may have maintained the support of Vietnamese and Latino voters in the district with his longtime support of working-class America issues and advocacy for immigration reform and victims of human trafficking.

Voting rights inquiries of vote dilution in the past typically concerned the suppression of vote choice of a single racial or language minority group living in a majoritarian white district. As districts continue to diversify, interracial and inter-ethnic vote coalitions increasingly need to be considered. While the 17th congressional district in California is a majority-minority district of Asian Americans, the findings presented here demonstrate that subgroups of Asian Americans based on country of origin exhibit political cohesion in divergent directions at the ballot box. While Chinese- and Indian-American voters formed a politically cohesive coalition of support for Khanna, Vietnamese Americans and Latino voters coalesced around Honda.

The finding illustrates that although the district is a majority-minority district of Asian Americans, the Asian-American community is not a monolithic voting bloc.

Sara Sadhwani is a PhD candidate in the political science and international relations program at the University of Southern California.