I believe you're referring to Fiorina's Culture War book.  It's an interesting read, but it's been discussed by a lot of people.

Here's an interesting piece here that addresses it:

http://www.thedemocraticstrategist.org/strategist/2006/06/polarized_partisans_probably.php

That's the book. Thanks for the link that provides a nice rebuttal -- that polarization has been increasing since 1970 is a strong counter-argument to be sure.

However, I don't think one can argue either-or positions here -- clearly the US political system is a complex system with numerous feedback loops. No doubt the increasing polarization that began in the 1970s has led to partisan redistricting which is causing additional polarization.