Under what conditions do individuals opt out of the political mainstream and vote for the far-right? Results of recent European elections seem to defy the expectations of the literature, as the far-right gained a large share of votes despite relatively “normal” economic conditions and the stability of institutional constraints. In this dissertation, I focus on the demand-side to uncover why some people with anti-immigrant attitudes vote for the far-right but others with similar attitudes do not when supply-side conditions are held constant. I argue that what separates these voters is how immigrants are perceived as incompatible with the host society. Specifically, I argue that individuals who have populist far-right attitudes and who deem immigrants as “other” because they are not integrated are more likely to vote for the far-right than are those who do not. I develop and test this hypothesis using original survey data collected in Germany. The multivariate quantitative analyses show that the far-right AfD vote is associated with the belief that immigrants are not integrated and a lack of confidence in Chancellor Angela Merkel. Analysis of open-ended responses of AfD voters confirms these findings. AfD voters say that they think immigrants are forging “parallel societies” and that they are concerned about the long-term impact of immigrants in Germany. AfD voters place blame on both immigrants themselves, who they perceive as not integrating, as well as on Angela Merkel, who they blame for allowing immigrants into the country. By uncovering the underlying motivations of “less extreme” far-right voters, the findings of this dissertation provide a greater understanding of the mainstreaming of the far-right and its electoral success in western societies with immigrant populations.