Hard to say for sure. I think we can say, though, that JFK himself may never have gone into politics. It's my understanding that Joe Sr. always intended for Jr. to be the one with a political career, so John might've gone on to do something else. Possibly a businessman, writer, and/or an actor. With that said, assuming Jr. is the "primary" (or at least first) of the Kennedy sons to enter politics, he'd be at least a bit different from his brothers. I believe I've read that he was a bit more racist than the rest of them, so while I doubt a Massachusetts Democrat would be virulently anti-Civil Rights, he might be more of a "law and order", conservative Democrat in that way. I once did an AHC thread where the goal was to have a Kennedy/Wallace (or vice versa) ticket, and one of the suggestions was to have Jr. as the Kennedy for precisely that reason.