How could he win without VA and PA?
If Obama wins VA (13 EVs) and PA (21), he still wouldn't win based on electoral math. That would carry Bush's 286 EV total down to 273 (-13 from VA; Kerry won PA four years ago, so that's a Dem hold). So McCain could still win rather comfortably, but he'd have to do an unlikely sweep of FL (27), OH (20), NC (15), MO (11), IA (7), NM (5), MN (10), NH (4), CO (9), NV (5), WI (10) and MI (17), thereby giving him 314 electoral votes (44 more than needed). (underlined means states Kerry won in 2004)
The problem with such equations is that the states generally move as groups. So for Obama to win PA and VA, but lose OH, doesn't really make sense. So for WI, MN, PA and IA (and maybe even MI) to still be competitive at this point in the 2008 race, while Obama's numbers aren't looking good in OH, spells some major problems for the Obamessiah. Doesn't mean he can't win, just that his chances are getting smaller.