The most frequently asked question I receive from non-Jews about Jews is, why are Jews so liberal?
The question is entirely legitimate since Jews (outside of Israel) are indeed overwhelmingly liberal and disproportionately left of liberal as well. For example, other than blacks, no American group votes so lopsidedly for the Democratic Party. And the question is further sharpened given that traditional Jewish values are not leftist. That is why the more religiously involved the Jew, the less likely he is to be on the Left. The old saw, "There are two types of Jews -- those who believe Judaism is social justice and those who know Hebrew," contains more than a kernel of truth.
In no order of importance, here are six reasons:
1. Judaism is indeed preoccupied with social justice (as well as with holiness and personal morality), and many Jews believe that the only way to achieve a just society is through leftist policies.
2. More than any other major religion, Judaism has always been preoccupied with this world. The (secular) Encyclopedia Judaica begins its entry on "Afterlife" by noting that "Judaism has always affirmed belief in an afterlife." But the preoccupation of Judaism has been making this world a better place. That is why the Torah (the Five Books of Moses) is largely silent about the afterlife; and it is preoccupied with rejecting ancient Egyptian values. That value system was centered on the afterlife -- its bible was the Book of the Dead, and its greatest monuments, the pyramids, were tombs.
3. Most Jews are frightened by anything that connotes right wing -- such as the words "right-wing" and "conservative." Especially since the Holocaust, they think that threats to their security emanate from the Right only. (It is pointless to argue that Nazism stood for National Socialism and therefore was really a leftist ideology. Whether that is theoretically accurate doesn't matter; nearly everyone regards the Nazis as far Right, and, therefore, Jews fear the Right.) The fact that the Jews' best friends today are conservatives and the fact that the Left is the home of most of the Jews' enemies outside of the Muslim world have made little impact on Jews' psyches.