Of course I would also claim that many liberal Catholics, particularly Ted Kennedy, were probably waiting to switch sides once the force of law was on their side.
Something that has never really occurred to me, but just clicks when I think of all of the hold-out Democratic politicians "coming out" for marriage equality in that orchestrated manner in 2013.
I think you probably nailed that one - at least as an explanation for why Ted Kennedy used to be 'pro-life.'
The real question and the one that we'll unfortunately never know is if John and Bobby would have had the same "evolution" as Teddy or is it possible they influence Teddy to stay pro-life.