Conventional theories of ethnic politics argue that political entrepreneurs form ethnic parties where there is ethnic diversity. Yet empirical research finds that diversity is a weak predictor for the success of ethnic parties. When does ethnicity become a major element of party competition? Scholars have explained the emergence of an ethnic dimension in party systems as the result of institutions, mass organizations, and elite initiatives. But these factors can evolve in response to an emerging ethnic coalition of voters. The author advances a new theory: ethnic cleavages emerge when voters seek to form a parliamentary opposition to government policies that create grievances along ethnic identities. The theory is tested on rare cases of government policies in Prussia between 1848 and 1874 that aggrieved Catholics but were not based on existing policies or initiated by entrepreneurs to encourage ethnic competition. Using process tracing, case comparisons, and statistical analysis of electoral returns, the author shows that Catholics voted together when aggrieved by policies, regardless of the actions of political entrepreneurs. In contrast, when policies were neutral to Catholics, the Catholic party dissolved.

传统的民族政治理论认为，政治企业家在存在民族多样性的地方形成民族政党。然而，实证研究发现，多样性对于种族政党的成功来说是一个微弱的预测因素。种族何时成为政党竞争的主要因素？学者们解释了政党制度中种族维度的出现是制度、群众组织和精英倡议的结果。但这些因素可能会随着选民的新兴种族联盟而演变。The author advances a new theory: ethnic cleavages emerge when voters seek to form a parliamentary opposition to government policies that create grievances along ethnic identities. 该理论在 1848 年至 1874 年间普鲁士政府政策的罕见案例中得到检验，这些政策激怒了天主教徒，但并非基于现有政策或由企业家发起以鼓励种族竞争。作者通过过程追踪、案例比较和选举结果的统计分析表明，天主教徒在对政策感到不满时会一起投票，而不管政治企业家的行为如何。相反，当政策对天主教徒保持中立时，天主教党就解散了。