This chart shows where McCain must gain, and where Obama must hold in order to get to 270.
States appear in order of Obama minus McCain margin. Width is proportional to Electoral Vote. It takes 269 to tie, 270 to win. The yellow states are very close and jumping around a bit with each new poll. Finally, the classification is based on my PoliticalArithmetik model, which directly estimates the margin, rather than Pollster's which estimates each candidate separately. So this should be very close to Pollster, but on close calls we may differ by a couple of tenths of a point, and that can sometimes shift a state from lean to tossup, or lean to strong if the state is right on the edge of a classification.