I wish people would read my books (and articles)rather then rely on an (edited)8 minute interview. Just reading the Wapo post would answer some of the misunderstandings above:

http://www.washingtonpost.com/blogs/monkey-cage/wp/2014/06/23/americans-have-not-become-more-politically-polarized/

Hoover Institute's Fiorina's logic fails. He faulted Pew's research for categorizing people as "middle" when they had "inconsistent" extreme views. Then he said the research showed the "middle" group was the largest, hence Americans aren't polarized. So the data he said masked real polarization he uses to claim the nation isn't polarized. Little inconsistencies are what detectives use to uncover truth. Journalists should pay attention to them too.

there's a lot of what Morris Fiorina how to say just didn't ring true. Firstly has he ever heard of Blue Dog Democrats? And what is the Republican equivalent? What is the Democratic equivalent of the Tea Party? What has changed is that there is a larger percentage of the population who are led to believe that politics should be the highest expression of an individuals ideals and not just a framework for compromise and administration which it traditionally has been. There is only where one side of the aisle that believes any sort of compromise is comparable to moral degradation.

Alan Abramowitz has demonstrated (repeatedly) that among the portion of the American population that 'matter' (they are interested in politics, and they vote) partisans are very polarized on a wide range of political issues. Other researchers have noted recently a substantial rise over time in the percentage of Americans who report that they would be very unhappy if their children married someone of the 'opposite' political party or ideological orientation. Workplaces, and even communities are divided by partisanship (particularly support or opposition to the Obama administration) at unprecedented levels. I've been impressed by the findings of Lilliana Mason's recent research (Rutgers) and encourage scholars and citizen scientists interested in the issue of polarization to take a look at her work.

Morris Fiorina just said that the majority of the American people "don't believe in Darwin".
What on earth does that mean?

Fiorina seems to making "a distinction without a difference"

Political parties used to have a greater diversity of opinion, now they are more "ideologically pure".

Part of what defines social groups is shared values and opinions. Having a diversity of opinions within a group allows for people to moderate each other's views. Instead, you get groupthink and an echo chamber.