From RCP:

A lot can change in just a couple months, and Sen. Arlen Specter (D-Pa.) knows this all too well. The five-term senator, who’s been a Democrat for four months, switched parties in April after realizing he would lose to Pat Toomey (R) in a GOP primary. However, Specter now trails the former congressman by double digits in a Rasmussen general election poll.
Toomey 48 (+9 vs. last poll, June)
Specter 36 (-14)