Why Is Pennsylvania Tightening?

Some thoughts:

1. Obama is on the air there now and his invisible army is organizing.

2. Clinton has been the major focus of the national press and the local press; the coverage has been unflattering; her mistakes are accumulating. There has been no corresponding attention on Obama's fitness for the office.

3. Obama spent five consecutive days in the state on a bus tour, and his campaign aggressively bracketed the visit with local news interviews and targeted local advertisements.

4., I don't like the phrase "natural tightening" because I think it's kind of dirty, but we've seen similar Obama "surges" in Ohio and California.