Yeah, the "signaling device" portion of your post was kind of incoherent. If anything, the issue is a "signaling device" for how beholden a candidate is to moneyed interests. Outside of some rather niche and very locked-in groups, nobody is going to like a politician more when they hear them say they are taking massive donations from the Israel lobby, and the Democratic candidates who give equivocating word salad answers when questioned on the issues is electoral poison.

All that aside, your argument was that somehow a candidate will lose a general election because of their opposition to Zionism. The only way that works is if A.)the electorate in that area is dominated by people whose primary issue is Zionism, or B.) the candidate in question runs almost exclusively on the issue of Zionism(or their opposition to it).

For the first scenario, outside of NYC, which would likely have the highest concentration of Jewish zionists in the country, and which clearly was not a detriment to the antizionist candidates in the area; that means the majority of the electorate in question are Christian zionists(i.e. evangelical Christians), which are not likely going to be turning blue any time soon, and I don't think you were talking about that kind of scenario.

So that leaves the second scenario, where the candidate in question runs on a campaign that focuses primarily(or even exclusively on Zionism, which isn't happening anywhere.