No, sadly we don't know that. Regardless of his voting record, Senator Santorum is personally responsible for getting a pro-abortion social leftist elected instead of a solid pro-life conservative and he may now be responsible for ensuring that a unified Republican government will be unable to get conservatives into the judiciary. This error could harm our republic far more than the good provided by any single voting record. The Senator would do well to remember that he will never be supported by the left and any political future he may have will come from the right. Conservative voters have long memories, often too long, and these voters will not soon forget these betrayals. Furthermore, a failure of the Republicans in the senate to deliver on their party's ideals during this time of united government they were given could marginalize the rank and file's support of the party for a generation.
He's not responsible for Specter getting elected. If anything, he's responsible for Specter getting the Republican nomination, because he's politically astute enough to know that Toomey couldn't win a statewide election in Pennsylvania.