Per TPM:
Republicans pilloried President Obama throughout the campaign for being a purportedly weak ally to Israel, but Election Day research suggests that the strategy flopped with Jewish voters.
The article cites a J Street poll giving Obama 70% of the Jewish vote, compared to 74% in 2008.
TPM talks about economy trumping Israeli security as a priority, but there are deep structural reasons why the GOP's brand is tarnished for American Jews. In a nutshell, the Republican Party embraces a Christian theocracy and is hostile to those who do not. No amount of warmongering on behalf of Israel or adopting Jews as honorary Christians (endless repetition of "Judaeo-Christian") can wash away the stink of Old World religious intolerance.
The history of European Antisemitism is part of the cultural identity of a great many American Jews. We learned at an early age about the progroms, the blood libel (that uber-theocrat Sarah Palin thought she could successfully exploit the term speaks volumes about the cluelessness of the wingnuts), and the ceaseless pressure to convert.
The Jewish identity in America, despite many decades of assimilation and movement into higher economic levels, is rooted in an uneasy sense of being an outsider. We've seen how a society can appear to have accepted Jews and suddenly violently turn against us.
Republicans trigger this spider-sense every time they claim that the country was Christian in its founding, every time they try to mold our laws based on their theology, every time they ostracize a community member who objects to mixing religion and government (especially when they assert that their private religion is a community-wide value!), and last but not least, every time they label a minority as a dangerous outsider.
While such things are not exclusively Republican or Christian (Pam Geller makes me so ashamed), the news is perennially full of conformist Republicans who cannot imagine that atheists or Muslims have a place in our society, reject science on religious grounds, and are homophobic and oppress women based on religious doctrine. They own the image, and occupy a key stereotype in Jewish thinking: the persecutor.
Perhaps further assimilation will change this, American Jews will one day no longer think of themselves as outsiders, and will no longer be more sensitive to intolerance than the general population. But that day is not here yet, and Republicans will be unable to make significant gains with Jews until they change, or we do.