Bob Casey is not "staunchly pro life." His stance on abortion is one of convenience, a way of getting elected. If elected, he'll march to the Democrat party tune.
I'm not so sure about him not being whole-heartedly ant-abortion. Remember, his dad, while govennor, was not allowed to address the Democratic Presidential Convention back in 1992 or 1996, because he was anti-abortion and wanted the Democrats to hear the other side. He may have become very solid over that. We may know for sure later, though.
Governor Casey was pro life and never waffled on the issue.
I doubt his son has a conscience of convenience on this issue.