I don't have a ton of time to go into this, but read Glenn Greenwald on an actual example of Pro-Israel lobbying organizations exerting a lot of cash and pressure to push towards confrontation with Iran. An important element of this, by the way, is that American Jews are significantly less likely than the median American to support either war with Iran or, when it happened, war with Iraq. But the organizations that speak for them, and raise money from them under the cover of a more blandly pro-Israel agenda, are quite hawkish. And quite effective.
In 1997, Fortune magazine asked Congressmen to rank the most powerful lobbying organizations in DC. In 2005, the National Journal did the same. Both times, AIPAC came in second -- ahead of, for instance, the AFL-CIO and the NRA. Now, we would never dispute the AFL-CIO's power within the Democratic Party, and we would never question the NRA's effectiveness on gun issues -- but we're supposed to pretend the organization that Congressmen think is more powerful than either have significant influence? It's silly. And when the framing is pro-AIPAC, and pro-its agenda, as Glenn Greenwald notes, there are no similar constraints. In that context, even The New York Sun can engage in such anti-semitic behavior as calling New York Jews the "ATM" for the Democratic Party and suggesting candidate will have to toe the AIPAC line on Iran if they want to make a withdrawal.