Changing established patterns of behavior is a difficult thing to do - I know that from personal experience, having once been a solidly Democratic voter. But over time, the "facts on the ground" do change, and people who are rational will change their behaviors to take that into account. The Republican party of today is very different from what it was 20 or 30 years ago. Likewise, the Democrat party of today is not the same party that it was 20 or 30 years ago. The Jewish population is also changing, with new generations acknowledging the world as it is today rather than the world as it was in their mothers' and fathers' generation. And, over time, there has been a corresponding shift away from the Democrats by Jewish voters.
I've had this conversation once. The long sad story of how Uncle Issy was kept out of Princeton in the thirties by some Protestant bigot, therefore Jews are Democrats Forever. Poor little prince.
I was tempted to add--"Well, my Cherokee grandma picked up chestnuts along what is now the Blue Ridge Parkway in the thirties so that she could have shoes to go to school...there was no hope for college for any of my family in that generation..."
But I didn't think he'd be impressed, since he was indulging in a ecstatic paroxysm of vicarious victimhood--thanks to pore ole Uncle Issy.
Maybe the real reason is that liberal Jews, and a lot of conservative Jews, too, like Krauthammer et al -- can't bear to rub elbows with Christians, and there are too many conservative Christians in the Repub party. We got a real eyeful and earful of what the real attitudes are during Gibon's release of "The Passion."