Adam Kushner at The Plank has a good post explaining, slowly, how it is that Jews don't flock to the GOP merely because they loudly trumpet their support of Israel.
1) Jews have other issues important to us aside from Israel, most of which the GOP is diametrically opposed to us.
2) Jews don't trust the motives of the Christian Right on supporting Israel, and remain unconvinced that their different motives won't lead them to supporting policy positions actually detrimental to the interests of Israel.
3) It seems like the GOP "pro-Israel" stance is to encourage them to adopt a hyper-militaristic stance that really isn't in their best interest. Because we, unlike the Christian Right, have a real stake in this conflict, we can't afford to lock Israel in perpetual combat with its neighbors to prove a point about toughness against Jihad. As so often is the case, the GOP is talking tough with other people's lives on the line.