In the debate Bush made the point that he was unpopular in Europe for standing up for Israel. A good column in National Review discusses Jewish support for Israel. It finishes by noting that if Jews vote for Kerry anyway, it will show future Demcocrats they have no need to support Israel and show Republicans they have nothing to gain by doing so.
I don't think that the President Bush's support for Israel is the result of a pandering attempt to obtain Jewish votes, as you seem to suggest. I think it is heartfelt and based on his religious and ethical make-up. He believes that it is the right thing to do.
Even if President Bush were supporting Israel in order to obtain votes (which I don't believe is the case), I think that the votes that he would have in mind are those of the evangelical Christians. Common belief is that some 4 million evangelicals stayed home in 2000 rather than vote for President Bush.
Liberal Jews, like all liberals, in many cases have a lifetime (and, indeed, generations of lifetimes)of belief in liberalism as a kind of secular religion. Although I myself am a passionate supporter of Israel, I don't think that you can expect lifetime liberals -- regardless of their religion -- to ignore their life and family commitment to liberalism just because of President Bush's support of Israel. Most American Jews have never visited Israel anyway.
I do think that all liberals who plan to vote for John Kerry are pathetically short-sighted for not supporting President Bush because of his fight in the war on terror. In my opinion, this one issue trumps every other issue, as Mayor Koch has said time and again.
Nonetheless, I do expect President Bush to get Jewish support in the upper 30s. I realize that this is higher than the AJC poll which puts support in the mid-20s, but I think that the poll is based on old data.