Extremism.

Greenwald:

The GOP debate in South Carolina two weeks ago was something of a watershed moment in American politics. It really was like watching a debate between Michelle Malkin, Rush Limbaugh, Glenn Reynolds and Michael Savage -- with the LGF commenters as the audience, cheering most boisterously for the most extreme warmongering, pro-torture and pro-lawless-detention sentiments. It is one thing to encounter that level of extremism in the right-wing blogosphere or on talk radio. But to see that embraced so openly and so eagerly by virtually all of the GOP presidential candidates is rather staggering, and self-evidently meaningful.