Significant research indicates that attitude change is often a product of partisan learning. However, as the party system continues to rearrange around issues of race and immigration, and as new racial policy issues thrust onto the agenda, it is unclear whether voters learn to adopt racial policy attitudes more based on race/ethnicity or on party identification. We evaluate the partisan-learning model versus a racial-learning model with regards to public opinion on sanctuary cities/policies among survey respondents in CA and TX. Given President Trump's public antipathy toward sanctuary cities, we argue and show that negative partisanship is the most plausible vehicle for sanctuary city attitude change between 2015 and 2017. In this particular case, we find no support for a racial/ethnic-learning model.