John McCain lost Pennsylvania because his campaign strategy in the state did not play out as planned:
1) McCain counted on older voters; Obama carried voters 65-and-above by a 51 percent to 48 percent margin. (Nationally, only 44 percent of the 65-plus age group counted thus far reports voting for Obama.)
2) McCain counted on working class white voters. Obama won whites with incomes under under $50,000 by a 52 percent to 47 percent margin. (Nationally, Obama is carrying 48 percent of this group.)
3) McCain also counted on drawing Pennsylvania voters who supported Hillary Clinton in the Democratic primary. Obama won 81 percent of Pennsylvania Democrats who preferred Hillary Clinton in the primary (Nationally, the figure is 85 percent).