You don't consider Santorum telling us himself that he was pro-abortion until 1990 "proof"?
For me to call someone prolife or pro abortion, I would have to see something that they wrote from that particular time period. It’s not usually too difficult to figure out, but you cannot rely on labels. I’ve been burnt in the past by labels.
I’ve worked with folks on both sides, and it’s my experience that a great many folks who label themselves one way, especially if they are not politically active, one way while actually affirming the opposite position.
What they lack is the political consciousness to understand what the label means - oftentimes taken things at first glance.