"Pennsylvania is vital to what Mr McCain calls his “narrow victory” strategy—eking out just enough votes in the electoral college to win the White House. If Mr McCain can capture Pennsylvania’s 21 electoral votes, he can offset Barack Obama’s gains in Republican strongholds in the Mountain West; if he loses Pennsylvania, his goose is probably cooked."
More at the Economist
Watch the Eastern States Election Returns. If Pennsylvania goes blue, then McCain is cooked, if Virginia goes blue not is he only cooked, he is well done, if N.C. goes blue, McCain is burnt to a crisp.