Once in office, what are the chances he'd get voted out? I'd guess pretty slim.
Slow down for a second to consider this:
Specter an entrenched 4 term incumbent.
Specter nearly lost the primary (I know, I know. Almost doesn't count.)
If I/we are successful in removing an INCUMBENT and replacing him with an opponent who would likely not have won without our help, don't you think that we can remove him if (A) he doesn't have our help next time, and (B) we actively support a solid conservative candidate against him.
What we did, in coming so close, in the face of the odds against us was nothing short of amazing. Three months before the primary it was Arlen Specter against WHO? It took the POTUS's visit to PA in the final week before the election for Specter to win in a squeaker (less than 1 1/2% -- 15,000 votes out of 1.2 MILLION).
This race taught me that there are a lot of people who want to support quality people like Toomey. That some of them caved under the weight of a purely political (rather than ideological) endorsement of an incumbent was extremely disappointing.
This race stirred people to action who have never been involved before. Part of my (unpaid volunteer) job will be to keep them stirred and ready to help the next good conservative to stand for election and help to awaken others to a new GOP that will stand for principle and not just ruling power with no regard for principle.