Empirical studies show a link between substantive and descriptive representation of racial and ethnic minorities. However, our understanding of the mechanisms through which this association operates comes almost exclusively from normative arguments. This paper examines three of these proposed mechanisms: two intrinsic mechanisms operationalized as perceptions of shared experience and a motivation to represent, and an extrinsic mechanism of electoral incentives. By doing so it moves on from documenting the link between descriptive and substantive representation, to explaining it. We find clear evidence that prospective minority representatives are influenced by all three motivations, to a different extent, with a difference between minority candidates of different parties. Also, while ethnic minority population of the constituency is usually associated with extrinsic motivation, we find it increases intrinsic motivation for minority representation among prospective minority representatives, suggesting these may be less distinct than it is assumed in the normative literature.