Two Blue-on-Blue: Mark Critz actually beat Jason Altmire in PA-12, and Tim Holden lost to Matt Cartwright in PA-17. Analysis in a little bit.
[One A Little Bit later] …yeah. Had to refresh my memory; but Holden losing to Cartwright is not really unexpected. The PA legislature cheerfully gutted Holden through the unique mechanism of shifting his district from R+6 to D+4; the Democrats in the new district responded by deciding that they don’t actually want a Blue Dog in that seat, and honestly, I can’t blame them over much for that. I can’t stand Blue Dogs myself. As for Critz v. Altmire… eh. Personally, I was rooting for injuries, but it’s surprising that Critz’s union pandering beat out Altmire’s sudden pro-choice pandering. I guess that they both couldn’t lose…
The more the Blue Dogs are pushed out, the more radicalized the Dem party becomes. The end result is the turning away by the voters. You could try to make this argument with the RINO extinctions, but I think there is a difference. This country is, by nature, conservative. Also with the failure of the Blue Model (which is all the Dems have to offer) people are no longer attracted to them.