The most plausible straw of hope for the McCain campaign is that undecided voters will lurch toward their candidate en masse. How plausible is that prospect? Not very plausible, if last night's CBS poll is accurate. The poll breaks down the undcided vote by ideology:

Liberal:         24%

Moderate:     51%

Conservative: 22%

Pretty balanced, right? Except the country as a whole is far more conservative. The latest Pew Research poll of likely voters produces a breakdown like this:

Liberal:         19%

Moderate:     34%

Conservative: 42%

(These numbers come from Michael Dimock of Pew Research.) In general, Democrats virtually sweep the liberal vote and win the moderate vote by a wide margin in order to be competitive at all. An undecided voter universe in which liberals actually outnumber conservatives, rather than being outnumbered by 2-to-1 as among the overlal voting base, is distinctly more friendly terrain.

--Jonathan Chait