ROLL CALL: Congressional Democrats’ Pennsylvania Problem.

As Democrats struggle to net 25 seats and win back the House majority in November, no single state reflects the party’s challenges more than Pennsylvania.

After all, Pennsylvania has gone Democratic in the past five presidential contests, and the apparent movement of the Philadelphia suburbs away from the GOP during the past two decades suggests a fundamental political shift in the state.

But if the southeastern corner of the Keystone State has started to resemble New Jersey and Connecticut, Western Pennsylvania increasingly looks like West Virginia or southeastern Ohio, areas where voters have started to think and behave more like Republicans. This movement of working-class voters toward the GOP has helped offset the partisan trend in the Philadelphia suburbs, keeping Pennsylvania an interesting and competitive state.

Just look at the way many counties voted in this year’s Democratic primary.