So why couldn't they in good years like 2006 and 2008?
The Democrats ran a third-tier candidate in 2008 and he nearly defeated Gerlach on Presidential coattails/anti-Republicanism alone.
No, Phil, elections in PA-6 won't go 58%-41% forever... but the difference between 2008 and future years isn't "Democrats win, or Democrats lose," it's that the margin of the D advantage will reduce along with the national margin. Maybe there will be a Republican suburban comeback in the northeast suburbs in federal races, but we haven't seen any green shoots for it yet.