The motivation for the model presented in the last chapter was the observation that changes in regime type in Zambia seem to co-vary with changes in the relative political salience of linguistic and tribal identities in national elections. During multi-party contests, ethnic politics revolves around language group divisions, whereas during one-party elections it revolves around tribal differences. Given this pattern of co-variation, it is natural to assume that it is something about the multi-party or one-party nature of the electoral regime that is driving the salient cleavage outcome. However, it is at least possible that other factors that happen to co-vary with regime type could be responsible for the changes we see in the salience of tribal and linguistic identities. If so, these factors would offer competing explanations for the argument presented in Chapter 5. The first part of the present chapter explores this possibility.

The second part of the chapter takes up another potential problem: endogeneity. Even if we are able to rule out the possibility that something other than regime change has caused Zambian politicians and voters to shift their focus from one ethnic cleavage dimension to the other, we might still have the causal arrows backward. It is possible that changes in the salience of tribal and linguistic identities, driven by factors other than changes in regime type, are what caused the transitions from multi-party to one-party rule and back. This possibility needs to be ruled out for the argument advanced in the book to hold.