He would also be the first major presidential candidate who has openly admitted to eschewing organized religion. That's still a pretty big 'no-no' in American public life, though I'm certain we've had agnostic, atheist, or ambivalent presidents before, including the last two. Back in the day JFK was attacked as a Catholic for having allegiance to the Pope over the U.S...Romney's Mormonism was used to some impact by those distrustful of the religion. I don't think Sanders will be attacked for having allegiance to Israel over the U.S. or for other Jewish stereotypes, that's for sure. I could see an attack on Sanders for being "Godless" and a "Socialist" though.
Sanders:
“I am Jewish,” Sanders told the Times’ (of Israel) editorial board when asked whether he believes in God. “I am proud to be Jewish. I was bar mitzvahed from the Kings Highway Jewish Center, a long time ago. I am not actively involved in organized religion.”