Why do Jews vote for Democrats? I'm asked this question often. The theory put forth by Republicans is that the Democrats don't support Israel, and the Republicans do. That's not quite right, but more on that in a moment. There are many reasons why Jews are Democrats, and stay Democrats, President Obama and Prime Minister Netanyahu disliking one another notwithstanding. The reasons Jews are overwhelmingly Democratic include tradition, anti-antisemitism, FDR and World War II, and Judaism itself.
Let's deal with one stereotype: All Jews support Israel. It just isn't true. There are many very religious Jews who don't support Israel based on Judaism itself. Their belief is Israel may only be established by The Messiah, and David Ben-Gurion was no Messiah. For them, the State of Israel is a poser, a pretender, illegitimate created by an unholy political alliance.
There are other Jews who think the whole idea of "Chosen" is hogwash, and all the existence of Israel does is set up another Holocaust, and Israel should be relegated to the History Books. In their view, a Jewish Homeland has always been, and always will be a problem. Their view of dealing with the problem is to not support Israel, forget the notion of Chosen, and to practice their brand of Judaism which is to remember traditions, and forget "chosen" and oppose a Homeland.
When Jews immigrated to the USA in substantial numbers, primarily to the Northeastern USA, Jews often encountered antisemitism and were relegated to low paying jobs. To counter business owners who wanted to exploit cheap Jewish labor, trade unions were formed by Jews, and in large numbers, so Jews entered the American Labor Movement. What do liberal parents often raise? Liberal children; so the children of children were taught liberal thought is correct thought.
In the 1930's, New York Jews started hearing of families disappearing in Nazi Germany. They went to President Roosevelt, the former Governor of New York, who listened to their stories of things going on in Germany. FDR told them he would love to do something about Hitler, but the Republican Party at the time were isolationists. In addition to isolationism, were cozy with Charles Lindbergh, a Hitler apologist, and National Hero, who supported Hitler.
Germans were and are to this day, the largest ethnic group in America, and the GOP pandered to them. It wasn't only Lindbergh who was influential with the GOP; industrialist Henry Ford, a notorious anti-Semite whose writings on the topic are used even today by anti-Semites to support their hatred of Jews, was very influential in the GOP.
His book The International Jew is second only to Hitler's Mein Kampf, in preaching Jewish hatred. The welcome mat was not out for Jews in the GOP. After the bombing of Pearl Harbor, FDR was only able to include war against Hitler because he had tied Germany and Italy to Japan as The Axis Nations. Had he not made that tie, the Declaration of War would have been only against the Japanese.
It wasn't until Richard Nixon appointed Henry Kissinger, a Jew, to high office things began to change between the GOP and Jews. More change during Reagan, although at times our relationship with Israel was strained, the Religious Right viewed Israel as not only our ally, but we had a religious obligation to aid and protect Israel.
Within Judaism, there is a Hebrew term "Tikkun Olam" which literally means "repairing the world". In Judaism, it is the spiritual purpose of life: to do good works, good deeds, and to help those who need help to have a better life. So that fits with the whole Democratic Party goal of social programs. In effect, it is government putting a Jewish spiritual obligation to work.
The entire premise that Democrats don't support Israel is absurd. President Obama certainly does. During his nearly 8 years in office, Israel has not been denied even a single bullet in Military Aid from the USA. In fact, President Obama increased military assistance to Israel and paid for half of Iron Dome. That latter program may be a violation of our ABM Treaty with Russia, but President Obama thought Israel was important enough to risk the fallout of a major treaty violation in exchange for Israel being able to protect herself from rocket attacks.
Jews are not a single issue group by any means. We are fully assimilated into America, and participate in a host of issues, Israel being one of them. However, the reception by the GOP of Jews coming into the party isn't always warm. There is an element of the GOP which is not thrilled to have us, and in fact are just as bigoted as they ever were. Ron and Rand Paul and their ilk, dislike Jews and Israel. Rand Paul moderated his views once he decided to run for President, but he did try to put an end to military assistance to Israel.