Nolan McCarty demonstrates that ideological polarization between Democrats and Republicans in Congress increased in the 110th Congress. See the graph above. He notes that this flies in the face of predictions that the 2006 elections would usher in a new, more centrist Congress, in part because some of the newly elected Democrats were Southerners, Blue Dogs, etc. Joe Klein, whose argument led to this Time magazine cover, comes in for a little drubbing.
To me, a driving factor in this particular instance of misguided punditry is that the news media loves conflict — as any textbook treatment of news-making will tell you. Conflict between Republicans and Democrats is okay, but conflict within parties is even better. This has been a recurrent theme during the fall and after the election. In particular, conservative Democrats, their potential defections from the party line, and their potential conflicts with a President Obama are a popular subject of discussion.
Nolan suggests, however, that the 111th Congress is likely to be even more polarized than the 110th, especially as moderate Republicans from outside the South have become even less numerous.