This is an old controversy, brought to focus in part by Walt and Mearsheimer article, but very acute now due to the current war in Lebanon.
The facts are that a) AIPAC does lobby for certain policies; b) for long time, these policies were largely adopted, now, they are adopted completely; c) AIPAC functionaries are on record bragging how they managed to defeat (usually, in primaries) opposing politicians.
Yet, the extend of the "AIPAC success" cannot be explained by the sum of their efforts. Notably, it seems that AIPAC is much more successful in convincing our elected officials than in convincing American Jews! Recall a recent lament of a Lieberman supporter that at least half of his Jewish constituents supports Lamont. Unless we understand the phenomenon of "AIPAC influence" we cannot rationally discuss it and more importantly, effectively counteract.
I would say that broadly speaking, there are two basic types of "influencing activity". Imagine a pre-industrial population without the technology to distill alcohol. One type of influence would be to market booze to those people, another would be to advocate temperance. You do not need a coordinated conspiracy of booze merchants to spread alcoholism, and even heroic pro-temperance effort may have meager effects. What would probably be least successful would be a pro-temperace effort concentrated on demonizing a single booze producer.
With this perspective, we can sketch the relevant matching pair:
convince a "pre-philosophical" population that they are superior to all others, than they can disregard the opinions of all others (kvetchings of the inferiors), and if things get rough because others disagree with us, well, we can always kick some ass
convince them that even if they were better, they should not behave if they were superior, as this is one basic mark of being better (e.g. being better, we should not torture the bad guys because one reason for being better is that we do not torture, etc.)
On issue after issue, the art of conservative politics is to identify what can serve as the booze for the population and market it profitably. For example, is it better to agree to some extra costs and limitiations on behavior and do something about global warming, or not? Can one have any hope competing with this approach?
Well, yes. As we know, temperance proponents can win elections in a largely alcoholic population -- not a sure thing, but it happens: part of the population does not look booze outright, more importantly, many alcoholics can be convinced that booze is bad for them. Sometimes the same person votes for "making the county/reservation dry" and keeps drinking, but recognition of the problem is a start of a solution.
To many of us, and the almost all wingnuts, Israel is our football team and she allows us to enjoy, however vicariously, exercising the superiority. The fact that we CAN disregard the opinions of others is not all that satisfying unless we do. The fack that we can "go there and kick the ass of the bad guys" is not all that satisfying unless we do. As we all know, it is much easier to delegate such actions to your favorite football team than to do it yourself.
So we can idolize Israel, denigrate the opponents, but is it really friendship, or the grooming of our gladiator? I guess that this is a better frame than "why are we ruled by a Zionist conspiracy". We would not unless we (and especially, the right wing) did not like it. And there is a long shelf of various booze brands in the bar.