Santorum knew that if the Republicans lost Spector in this seat, it could affect the outcome of Bush's judicial appointments, so that was why he did it. I agree with Santorum under that circumstance.
Toomey would have voted the right way as a regular habit. Someone else could have been appointed to the Judiciary Committee who would have done the same thing or better than Specter on appointments.
Jon Kyl was on that committee too and he could have stepped up into the Chairmanship and later Ranking Member. In fact, Jeff Sessions (who is also excellent) did move up into that position. Both of them would have been a thousand times better than Specter.
Sadly, after disappointing everyone on MANY issues after Bush and Santorum bailed him out in the primary, Specter publicly said that Bush needed to nominate people who would not try to overturn Roe v. Wade which was opposite of Bush's and Santorum's position and then changed to the Democrat Party.
It has left a bitter taste and it's too bad, but that's reality.