Obama snuck up on them so quickly in VA and has such a huge advantage on the ground that it's no longer realistic for the McCain campaign to organize and turn it around. There's also mathematical reasons for giving up on VA. 13EV simply isn't enough to push McCain to 270. He would need to win CO, NM, NV and MO also and there's virtually no statistical chance of that happening at this point. Chances are, at worst, Obama wins 2 out of the 4. (CO & NM most likely) Here's another math problem for McCain/Palin: If Obama wins VA, NM/CO/NV/MO are still not enough. In fact, even if you give them 1EV from Maine it's still not enough. (3EV short)
Here's where things start to look impossible for McCain. He needs to win PA, a state that broke heavily towards Obama 3 weeks ago and has shown no signs of turning back, and here's where it gets hard: He STILL has to find 13 more EV to win it.
Their last hope is to win 13 EV out of the following states: NV, NM, CO, MO. A total of 30 EV. Unfortunately for McCain, again with the math, it's not really 13EV. It's actually 16EV because no combination of these states gives you 13EV. The closest you can get is 16 (MO+NV) McCain might, as an extreme longshot, be able to pull 1EV out of Maine however MO + 1EV still isn't enough (1EV short guys, sorry)
So that's where we stand today: McCain must carry PA, MO and NV to win this election.
NV is winnable. MO is hard to figure. Not a lot of polling there in the last few days. One outliner suggests McCain is doing better there than previously polled. I guess the logic there is if PA goes red, MO would follow (same demographic principals) However this strategy fails to anticipate Obama's strong support in IA. This is another state Obama has run away with over the last month. Whatever groundswell of support allowed Obama to surge in IA is surely effecting MO too. Plus of course, flipping PA this late in the game given Obama's surge there is also incredibly hard.
Oh and this assumes Obama doesn't just win one of the following states: OH, FL, IN, GA, NC. If he wins even one of those it doesn't matter what happens in PA/MO.
It's not over yet. It's close though. Look at McCain's numbers in PA, MO, and NV at the end of the week. That should tell us if there's even the most remote chance he can make a play at it.