I'd also say the same if asking about those identifying as Republicans who sincerely harbor anti-Semitic beliefs. I have no "proof" of this -- neither do you.

The first thing one has to do is stop conflating all anti-Israel concerns with anti-Semitism. Absolutely the two CAN overlap and one can be an excuse for the other --- and is for plenty of people --- but certainly not all. Who among us really know how many? This sentiment also holds true for those identifying as Republicans or more conservative. A devout Christian should not in any way be anti-Semitic -- just based on clear, Christian principles. Christians can also be very supportive of Israel OR less so -- and it shouldn't conflate with being anti-Semitic. Yet, the reality is that that historically -- and I have experienced this firsthand as well -- there are Christians who express their unwavering love for Israel based on Biblical beliefs, but look at Jews in a particularly nasty way because they see Jews as purposely rejecting Christ, worse in some ways than any other group of non-believers. So one can be a fervent supporter of Israel for certain reasons but still have pretty awful feelings toward Jews in general. So I would caution about really convincing yourself that somewhere in the neighborhood of a quarter to a third of voters of any major U.S. party is actually anti-Semitic ----- unless you think this is the number across the general population (which seems quite high to me).

I'm only one person, but I am also Jewish and have my share of experience both as a child and adult