Fig. 3.

Tipping points in the level of intolerance. The tipping point for intolerance is similar to the dynamics in Fig. 2. A and B show the phase transition for two values of party identity, $\beta$ = 0.3 and $\beta$ = 0.5. Beyond a critical point $C_P$, a subsequent increase in political tolerance will not bring the parties back together (A) or reduce extremism (B), unless the level of intolerance has dropped far below the level at which polarization increased. C and D show that an increase in party identity shrinks the size of the hysteresis loop by reducing $C_R$ even further, approaching the point of bifurcation at which polarization cannot be reversed.