These models describe decision-making roles, not the demographic identity of the officeholder. Descriptive representation asks whether representatives share characteristics or experiences with constituents; substantive representation asks whether they advance constituents' interests. A member can be descriptively representative while acting as a trustee, or lack a shared background while acting as a faithful delegate.

Electoral incentives affect which role is attractive. Clear and intense district opinion, an approaching election, or a highly visible vote can push a member toward delegate behavior. Low-salience or technically complex questions may leave more room for trustee judgment. Party commitments, committee specialization, donors, organized groups, and national conditions also shape legislative choices.

In an application item, look for the reason the member gives. Following district instructions signals a delegate; relying on personal judgment despite contrary polls signals a trustee; varying the approach by issue signals a politico. Do not assume that casework, pork-barrel advocacy, party-line voting, or incumbency by itself establishes one representational model.

Video lesson: The Bicameral Congress: Crash Course Government and Politics #2