David Bernstein is talking about the 11 Commandment of Judaism over the Volokh Conspiracy. Part 1 is here and Part 2 is here. For those not in the know, the 11th commandment in Judaism is "Thou shalt not vote Republican." (For Republicans its "Thou shalt not run against another Republican".)
My Girl Amybear's dad is a big Republican. Her immediate family tends to vote to the right. The prominent Jews I work with are also Republicans, but I work for the military so trends tend to skew that way anyway.
It has always surprised me that a lot of very conservative religious Jews vote Democrat. You would think that the "family values" and the faith-based initiatives of the Republican Party would appeal to such a religious people, but no such luck. I think there are basically two reasons.
The first is that Jews tend to be very intimidated by evangelical Christians. Jews as a whole don't really try to convert people and evangelicals are all about evangelizing and converting. Big culture clash there. When they see a family member convert, chances are its the evangelicals "fault." When Jews see their kids converting they think about their culture dying because Jews do not see Jewish "Messianic" Christianity as a true extension of Judaism.
Also historically Christians converting Jews have also done so under the auspices of things like the Inquisition. It doesn't really occur to Jews that there were Baptists like me being put to the Question right next to their great-great-you-get-the-point-grandfathers. Jews as a whole don't understand the denominations within the Christian church very well, just like Christians don't really understand the difference between a Conservative and Reform Synagogue. What they do see is that the people acting very "christian" have often given Jews a reason to move someplace else or else.
The second is that Jews are a minority culture. When Christians start talking about faith-based initiatives, Jews realize that anything they do is going to be overwhelmed by the vastly Christian majority. Plus minority cultures tend to look to the government to safeguard their rights, which inherently puts them in the Democrat camp. The only one preventing tyranny of the majority is the government. That's a big reason why African-Americans vote Democrat and I think its a big reason why Jewish-Americans do too.
There are probably other reasons or other facets of these two that I haven't covered, but that's enough for now.
UPDATE: Matthew Yglesias has some commentary on it too. Its quite good and nice to hear from the other side of the aisle. He basically thinks Bush is too christian and that regionalism plays into it because the Jewish population centers tend to be in "blue" states. He's probably right on both counts.