Will Liberals Really Stay At Home?

In the wake of the proposed tax cut deal, Nate Silver wonders how Obama's base will react:

[J]ust because liberals are disappointed with Mr. Obama does not necessarily mean they will fail to turn out and vote for him when the only other choice is a Republican. In some ways, it probably helps Mr. Obama that the country has become so polarized and that liberals view Republicans as such an unacceptable alternative, and vice versa. The prospect of a President Palin or a President Gingrich would surely motivate most liberals to vote and even comparatively moderate Republican candidates like Mitt Romney will be under pressure to show their conservative stripes during the Republican primaries and are likely to campaign on policies, like a repeal of the health care bill, that liberals overwhelmingly object to.