Why does the United States support Israel?

Admittedly, I have my own personal biases in the Israel/Palestinian issue, but I have always wondered why there is such a close relationship between Israel and America.

From an economic perspective, a closer relationship with the Arabs would seem more logical, as their oil is far more important than whatever Israel provides. Instead, we align ourselves with the Arabs' most prominent enemy, and the results were seen in the 1970s oil crisis. Politically, the US isolates itself, as the vast majority of the world is highly critical of Israel. Even Europe seems to side with the Palestinians, and arguably abstains from anti-Israel UN resolutions due to pressure from the US.

Criticizing Israel in the US is political suicide, but why? Most Americans support Israel, but aren't Jewish, so why do they? Some argue that its due to messianic beliefs about the return of Christ, but that doesn't explain why less religious groups (i.e. the Democrats) also support Israel. Others talk of the media possessing a strong pro-Israel bias, but explain it with the age-old conspiracy of a Jewish-controlled media (being suspicious of most conspiracy theories, I have trouble believing this one).

In short, the US's support of Israel, which is in contrast to most world opinion, seems rather illogical. From an economic and political perspective, aligning ourselves with Israel's opponents would make more sense, so why isn't this the case?