Two moderate Blue Dog incumbent Democrats lost to left-wing, union-backed challengers in Pennsylvania yesterday:

The Blue Dogs’ bark in Congress is sounding more and more like a whimper.

The once-powerful coalition of conservative Democrats suffered two more casualties on Tuesday as Rep. Jason Altmire, D-Pa., lost to fellow Democratic Rep. Mark Critz, and Rep. Tim Holden, D-Pa., was ousted by political newcomer Matt Cartwright….

Holden, a ten-term congressman, had successfully fended off GOP challengers for years. But Pennsylvania mapmakers redrew his district to be more Democratic and he lost to a more liberal challenger. Similarly, labor unions propelled Critz past the more moderate Altmire, who voted against President Obama’s health care law.

It was a big win for the left-wing of the Democratic Party:

Even more than the defeat of three-term Rep. Jason Altmire by the more liberal Rep. Mark Critz in the re-carved Western Pennsylvania district, the upset of 20-year Rep. Tim Holden by political newcomer Matt Cartwright sent political shock waves from the Keystone State throughout the nation. In becoming the first incumbent House Democrat to be defeated for renomination by a non-incumbent, Holden–like Altmire–was clearly being punished for showing a bit of independence from the Obama-Pelosi-Reid line.  The self-styled “blue dog” Democrat had supported the Republican energy policy, which calls for more oil drilling and coal exploration as well as experimenting with alternative sources of energy.  In addition, Holden had opposed ObamaCare and, like Altmire in his race with Critz, was fiercely attacked by the far-left within his party.

The two moderates were targeted to push the party further to the left:

Getting a progressive Democrat into Pennsylvania’s newly redrawn 17th Congressional District was a priority for progressive groups, including MoveOn and the League of Conservation Voters. The latter ran the largest independent expenditure campaign in the race, which included a $230,000 TV ad buy on broadcast and cable networks in the Scranton media market.

The Blue Dogs always were an uncomfortable fit in a Democratic Party pushing ever farther to the left, increasingly comprised of crony-capitalists, union lackeys, and Occupiers.