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.
Dickson and Scheve. 200?. Social identity, political speech, and electoral competition. Forthcoming in Journal of Theoretical Politics.
"Much research in political science suggests that social identity can be an important factor in motivating behavior. If voters care about social identity, when will politicians find it in their interests to make group-based appeals? Do social identity concerns affect the policy platforms offered by candidates? In a model of political speech and electoral competition, in which voters care about both social identities and policy, we demonstrate that social identity concerns can lead to platform divergence even when the policy dimension is uncorrelated with identity. Further, the need for candidates to resort to group-based appeals depends on such factors as the relative sizes of social groups; the policy preferences of group members; whether candidates care about policy and if so, their preferred policies; and the extent of individual identification with groups. The analysis demonstrates that social identity can have a striking impact on the strategic conduct of campaigns."
Basically, social identity can add an additional dimension to an otherwise one-dimensional political space.
Research on similar subjects