Chait answers my question:
Congress is representing the generalized pro-Israel feelings of the public, which are strong, as opposed to their ambivalent views of the Flotilla incident, which are weak. In an environment where public opinion is overwhelmingly pro-Israel, and when asked about a specific incident involving Israel, two-thirds of the public is either favorable to Israel or uninformed, the expected outcome is for Congress to support Israel.
And when the US public was clearly divided over the assault on Gaza - even Rasmussen found a 44- 41 split in general and opposition to Israel's assault reached 51 percent among Democrats - the Congress backed Israel in a resolution by unanimous consent in the Senate and with only 5 dissenting votes in the House. That was a function of Congress' reflection of popular opinion? Please. While half of Democratic voters were against the war, Democratic senators were unanimous behind it? Can Chait offer another example of such a massive discrepancy? There was more Democratic opposition to the Iraq war than to the Gaza war, which even Israel now concedes was beset with war crimes on its side as well as Hamas's. Chait is second to none is seeing through bullshit, except on this question.
I don't doubt that in any abstract conflict between "Arabs" and "Jews", Americans are likely overwhelmingly to back "Jews," and given the nature of Israel's democracy and the autocracies in most Arab states, I don't disagree. But the overwhelming nature of Congressional majorities on this question needs explanation. It's obviously a function of an extremely committed and affluent lobby - which distorts US foreign policy on Israel (and, via a different lobby in a different context, Cuba) against the interests of the US. My view is that we should try to avoid that kind of distortion. On Israel, Chait doesn't.