Moving further away from the out-party

Two things are often stated about American politics (most vociferously by Mo Fiorina): political elites are increasingly polarized, and that the issue positions of the masses haven’t budged much. Assuming such to be the case, one expects the average distance between where partisans place themselves and where they place the ‘in-party’ (or the ‘out-party’) to increase. However it appears that the distance to the in-party has remained roughly constant (and very small), while distance to the out-party has grown, in line with what one expects from the theory of ‘affective polarization’ and group-based perception.