Cook's point is that most Democrats will vote for Obama, most Republicans will vote for the GOP candidate whoever s/he is, and the election will be decided by independents who actually look at both candidates and decide between them. Superficially, that sounds right.
I say "superficially" because Cook leaves out the voter intensity issue. Will Republicans and Democrats be equally motivated to vote? I think not. In 2008 anti-Bush Democrats were more motivated, in 2012 anti-Obama Republicans will have the intensity to be sure to vote.
Cook's argument is that Republicans will nominate an extreme candidate, unattractive to independent voters. He suggests Bachmann or Perry as extreme candidates. The result, an election between a poor performer (Obama) and an extreme GOP candidate.
I wouldn't be surprised if Cook is correct, about independents. Result: low voter intensity, among independents. Then the issue becomes voter intensity among party members.
Republicans are really bummed about Obama, to a lesser extent so are many Democrats. Thus Republicans will win in 2012, as they did in 2010, based on voter intensity.
