Fig. 7.

Increasing Democratic responsiveness to liberal policy mood swings. Democratic elites gradually become more responsive over time to policy mood swings throughout the 1960s and 1970s, as modeled by the time-varying $U_d$ plotted in A. The other sensitivity thresholds are $U_r=L_r=L_d=0.45$, as in Fig. 6. All other parameters and initial conditions are the same as in Fig. 6. (B and C) The resulting policy mood inputs $I_r$ and $I_d$ (B) and response of ${\alpha }_r$ and ${\alpha }_d$ (C) to these policy mood inputs. (D) The qualitative trends in ideological positions and the asymmetry in the polarization can be compared to the DW-NOMINATE scores in Fig. 1; see Fig. 8.