Here is an article in Tablet which makes that point in historical detail and far more eloquently than I did. Democrats are clearly the more secular party; Jews fear the GOP's overt Christianity. As the article makes clear, the key question for American Jews is the nature of America, not the future of Israel.
The best the GOP can hope for is that substantial numbers of Jewish voters stay home or vote for Ralph Nader. In a key state like Florida that could be important.