Doesn't necessarily make them antisemites, but it's fair to say that political opponents raising the issue aren't doing it because they think it's an asset. Presuming he wins, I disagree with the idea that this "kills" his Presidential ambitions. These issues will come up, better he deals with them now. If the worst he has in his past is are Jewish parents, a teamate who says he used the n- word, and a Confederate flag on his locker, pickup (did he have a pickup, that's another negative), whatever, he's in pretty good shape. This is old news six months from now, by raising it as a national issue, old news beyond Virginia.
I don't see why Jewish ancestry should be a problem with the voters. The problem is if he/she is a secular-liberal politician, rather whether he/she is Jewish ornot.
On the other hand, being a German-Catholic, conservative American may have strong negative consequences, since there are three strikes against it and 3 strikes and you're out!!!!!!!