Marc reports:

Pennsylvania will see a lot of Sen. John McCain and Gov. Sarah Palin next week.

The scheduling reflects McCain's tough electoral math. With some -- though by no means all -- advisers all but conceding Colorado, McCain would be forced to win a blue state in order to recoup the electoral votes. New Hampshire wouldn't give him enough, and Pennsylvania, the McCain campaign believes, is the most brittle of the remaining states. Public and private polls give Obama a double digit lead in the state, but McCain advisers believe that Obama is underperforming in the suburbs and exurban counties around Pittsburgh. Tensions between the two campaigns in the state is acute.

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