Stuart Rothenberg provides a worthwhile perspective at CQpolitics.com on the importance of Pennsylvania as a bellwether state for the strength of Republican candidates in November.

A few key excerpts:

There are many states that will have ballots chock-filled with exciting and competitive races, but if you are looking for a place where a big GOP political wave might show up early in the evening of Nov. 2 — or for evidence that it won’t be as big as some Republicans hope — you could do worse than focusing on Pennsylvania. […]
While polls conflict, Toomey and Sestak generally have been running about even. Toomey usually appears the more poised of the two candidates, and Sestak is likely to be on the defensive over the economy and his voting record. While the race is a tossup, it’s a bit easier to imagine Sestak, who has earned the reputation of being a difficult person to work for, imploding. … A solid Toomey win would be a bad sign for Democrats down the ballot. […]
Of the eight Democratic seats, Sestak’s open seat and Kanjorski’s now appear to be the best opportunities for Republicans. Former U.S. Attorney Pat Meehan (R), who is running against Democrat Bryan Lentz in the open seat, and Hazleton Mayor Lou Barletta (R) are experienced in the limelight and now benefit from strong poll numbers. […]
In the 12th district, where [Mark] Critz won a special election, Republicans hope for a reversal of that outcome in November. It certainly isn’t likely, but in a large Republican state wave, the district can’t be ignored.
Finally, [Patrick] Murphy faces a rematch against former Rep. Mike Fitzpatrick. Murphy nipped the Republican in a horrible year for the GOP, 2006, so the changed political environment certainly makes this a race to watch, especially in a wave.

Mike Fitzpatrick is in a tough spot against Pat Murphy, who was rewarded by Democrat leadership with John Murtha’s old Appropriations Committee spot earlier this spring.

This is a district where anti-incumbent sentiment will likely not be enough to flip the seat. Fitzpatrick will likely need Rothenberg’s wave, or a serious error from the Murphy camp, in order to win.