This could be another district where McCain's coattails help the GOP challenger. Considering how flukish Altmire's win was, some voters may still think of Hart as the incumbent.
It wasn't a fluke; it was firmly a part of the wider trend.
How many people predicted an Altmire win in 2006? IIRC, very few folks correctly called this race. I predicted an Altmire win, but I also said Gerlach would lose. As Keystone Phil and others would say, Hart lost because of her own lackadaisical approach to campaigning. After routing Democrats by huge margins in every House race (including her open seat win in the more Democratic version of this is CD), Hart probably assumed that she had solidified her hold on this district. Consequently, she refrained from running negative ads till the last few weeks of the campaign.
If Hart had followed Gerlach's lead and defined her opponent early on, say, after a nearly broke Altmire barely won the Democratic primary, she would've held this seat. Gerlach, Wilson, Pryce, Ferguson, and Reichert all proved in 2006 that scorched earth campaigns work.
Finally, the very fact that Hart, the consummate campaigner, was taking drumming lessons instead of fundraising during an election year is quite flukish.
