ch. 1. Introduction -- ch. 2. Conditional political learning -- pt. 1: The participatory effects of media choice. ch. 3. Broadcast television, political knowledge, and turnout -- Appendix to ch. 3. Measuring political knowledge, NES 1952-1968 -- ch. 4. From low choice to high choice : the impact of cable television and Internet on news exposure, political knowledge, and turnout -- Appendix to ch. 4. Description of knowledge measures -- ch. 5. From low choice to high choice : Does greater media choice affect total news consumption and average turnout? -- pt. 2: The political effects of media choice. ch. 6. Broadcast television, partisanship, and the incumbency advantage -- ch. 7. Partisan polarization in the high-choice media environment -- Appendix to ch. 7. Using a selection model to simulate partisan vote strength in the full electorate ch. 8. Divided by choice : audience fragmentation and political inequality in the post-broadcast media environment.