So a position of full throated support for Israel, no matter what the Israeli government does, is not a winning position, among "We The People".

And I don't think any Jewish leaders are asking El-Sayed to move to "full throated support for Israel, no matter what the Israeli government does." They're asking him to repudiate Piker and moderate his rhetoric, and warn that he risks losing support among Jewish voters if he doesn't. Not because Jewish voters invariably offer completely unconditional support for the Israeli government, but because Jewish voters are concerned about anti-semitism and overwhelmingly support the continued existence of a Jewish state (roughly 90% of American Jews, even while fewer than 40% self-identify as "Zionist").

And again, the point is that the Jewish leaders who are withholding support for El-Sayed aren't doing so because they want the Democrats to lose the seat. They're doing it because they want El-Sayed to change his position. Not to the position you describe, but to one that is more protective of Jewish interests in the U.S.