Considering that Biden is as pro-Israel as it gets for a Democrat, this is none too good for him. Imagine what would have happened had Sanders gotten the nod.
I'll hazard a guess. A bunch of people would claim most Democratic-leaning Jews were suddenly single issue voters who'd switch to Trump to support Netanyahu (who underperforms with reform Jews at home and seems to be far less popular in the diaspora for fairly obvious reasons). Another group would claim "descriptive representation" would mean the opposite (and they'd be wrong, because it's overhyped). There really wouldn't be much of a difference at all; perhaps the slightest of Republican trends if it boosted turnout in more conservative Jewish communities, but I strongly suspect this effect would be more significant in the evangelical Christian community if it manifested. I also suspect any attempt to generate Republican capital out of vague ties to antisemitic politicians would be cancelled out by the grassroots antisemitism which would flourish within the Republican campaign were Sanders were the nominee.
