Specter looks doomed even with the 3 conservative opponents.
But I don't see clear evidence that Specter will be defeated with the conservative "anti-Specter" vote split among many candidates, which is what Arlen Specter is probably banking on. Peg Luksik, Larry Murphy, and Pat Toomey are all currently seeking the nomination, and all three are known conservative candidates who have run statewide before (two of them against Specter -- Murphy was his '98 opponent and Toomey was '04)
Can Rassumussen point to a poll where Specter is losing by a clear margin with a "If the election was today and the candidates were Pat Toomey, Arlen Specter, Peg Luksik, and Larry Murphy, which would you vote?" scenario? Because that's the situation right now. I sure hope Specter is still trailing in such a scenario, but I have doubts. With RAT and Indy crossover and the "moderate" country-club GOP voters, Specter could probably pull 40% in a 4-way race, which is enough to win if the remaining 60% is split among 3 conservatives.