Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Posner. 2005. Institutions and ethnic politics in Africa. Cambridge: Cambridge UP.
Ethnicity is multidimensional in Zambia. On the one hand, people can choose to see ethnicity in terms of their tribal membership (there are over 6 dozen tribes). On the other, they can associate themselves with one of four language groups. [To me this sounds nested, not multidimensional.] Under what conditions are Zambian politics a competition among tribes vs a competition among language groups? In other words, what makes each type of identity salient?
People vote with their ethnic group "because of the widespread expectation that politicians will channel patronage resources to members of their own ethnic groups." This is backed by survey data, focus groups, elite interviews, and content analysis of speeches, newspapers, and other sources. As a result, politicians make frequent ethnic appeals, and voters make ethnic votes.
This seems to depend on political institutions. Since institutions change the boundaries of the political arena, they also change the choice. Tribal identities have tended to dominate during one-party rule, but linguistic identities have tended to dominate under multi-party rule.
Research on similar subjects