The purpose of this dissertation is to assess the degree to which state legislators are responsive to their various constituencies. The guiding research questions are: 1) Under what circumstances are state legislators most responsive to their districts, parties, and interest group supporters? 2) What drives certain legislators to take extreme issue positions? And 3) What explains and what are the consequences of state legislative polarization? I propose a theory of conditional responsiveness that specifies circumstances (issue type, electoral competition and legislative professionalism) under which responsiveness is most likely to occur. I systematically test my hypotheses using an original data set that includes information on over 4,000 state legislators and their districts in 30 different states.

I find legislators to be most responsive to constituents on high salience social issues. On lower salience economic issues, state representatives are much more responsive to their interest group supporters. In addition, I find members from electorally safe districts to be most responsive to their districts as safe members are more likely to reflect their district's demographic and political homogeneity. Legislative professionalism if found to enhance responsiveness. This discovery supports the view of many scholars who saw the professionalization of state legislatures in the latter half of the 20th century as a healthy development.

Across the country, I find a good deal of ideological extremism among state legislators. This legislative extremism, when aggregated, results in chamber level polarization. This polarization cuts into the productivity of the legislatures, making stalemate a more common legislative outcome.

Policy responsiveness occurring in state legislatures is a reassuring finding; responsiveness, however, is conditional. Certain conditions influence the degree to which constituency opinion really matters. Perhaps the most important condition is the level of public interest on a given policy issue - when people care, legislators respond. This observation has practical implications for our democratic system of government. Representatives, without an informed or caring citizenry, can get away with straying from the wishes or needs of their constituents. As such, a necessary component of representative democracy must be an informed and vigilant citizenry.