He's not the only one saying this. Here's The American Thinker making a similar claim, as well as Anti-Liberal Zone.
Noah Pollak appears to be the source, linking to this May 2007 interview with Professor Power. I've bolded the part they think is important, but I include the entire question for context:
Q. Though some analysts see U.S. foreign policy woes as a recent phenomenon, you argue that recent foreign policy missteps by current U.S. leaders have exposed and exacerbated long-standing structural and conceptual problems in U.S. foreign policy. Please explain.
Power: It is tempting to see Iraq as the source of all our woes now, whereas I see Iraq as the symptom, in some measure, of a number of longstanding trends and defects in American foreign policy.
One example is the US historic predisposition to go it alone. Because we have long undervalued what international institutions have to offer, we believed that we could go into Iraq, and as soon as we declared the mission accomplished, we expected to be able to turn the problem over to others, regardless of how they had been treated in the run up to the invasion. This thinking is very flawed, but not all that new. In a uni-polar world, the Clinton Administration was able to get away with an instrumental relationship with international institutions, but that is harder with the rise of new powers who are willing to challenge the United States in international bodies. It is also harder now that the Iraq war itself has exposed so many US weaknesses.
In addition, we long saw international authorization as a luxury, something good for global public opinion, but not very relevant to US national security. But what we have seen, by revealing our indifference to international legitimacy both in the Iraq war and in the practices carried out in our counter-terrorism efforts – the disavowal of the Geneva conventions, prisoner abuse, extraordinary rendition, etc. – is that being seen to thumb our nose at international law actually has profound security ramifications, as more and more people seek to take up arms against U.S. citizens and interests.
Another longstanding foreign policy flaw is the degree to which special interests dictate the way in which the “national interest” as a whole is defined and pursued. Look at the degree to which Halliburton and several of the private security and contracting firms invested in the 2004 political campaigns and received very lucrative contracts in the aftermath of the U.S. takeover of Iraq. Also, America’s important historic relationship with Israel has often led foreign policy decision-makers to defer reflexively to Israeli security assessments, and to replicate Israeli tactics, which, as the war in Lebanon last summer demonstrated, can turn out to be counter-productive.
So greater regard for international institutions along with less automatic deference to special interests – especially when it comes to matters of life and death and war and peace – seem to be two take-aways from the war in Iraq.
This is not the W&M hypothesis. At worst, it's a very diluted form of their thesis, in that it argues that sometimes the US listens to pro-Israel special interests, and that sometimes leads to bad results. This, she says, is emblematic of a broader, systemic flaw in how the US conducts foreign policy -- we let special interests construct what the "national interest" is and it leads us away from where we ought to go (Contra Pollak, it is not arguing in any way that Israel was responsible for America's war in Iraq).
W&M, of course, argue that US foreign policy in the area is controlled by the "Israel Lobby", and more importantly, that this is a unique exception to the way foreign policy decision-making operates. Far from being emblematic of anything, the Israel Lobby, from W&M's Realist stance, represents a dangerous exception to the Laws of the International System, which dictate that nation's have fixed and concrete security interests and always pursue them. This exceptional quality is the key reason why W&M's thesis is so offensive -- it's essentially an argument about Jewish hyperpower. But that makes it qualitatively different from persons (like Power) who believe that many factors beyond bare security interests influence how foreign policy operates, and observes that special interests advocating for Israel are one of them.
It is, of course, possible that Power has written something more directly on point that affirms W&M's hypothesis. But I highly doubt it, seeing as they come from drastically different schools of thought on international relations. W&M's thesis operates from a premise that Power doesn't share -- namely, that domestic, moral, or transnational forces never exert meaningful influence on foreign policy. Power appears to believe the opposite -- that these factors are extremely important influences on foreign policy decision-making (for good and for ill).
UPDATE: I sent Paul an email and asked for clarification. He responded with another Power quote, that her version of a sound mid-east policy would require "'alienating a domestic constituency.' That's close enough to the Walt-Mearsheimer thesis for me."
Not only is that not even close to the W&M thesis, it borders on being a truism. Americans (including Jewish Americans) have differences on what we want our mid-east policy to be. For example, I suspect Paul and I differ significantly. One of us is going to be alienated by whatever proposal ends up being adopted. If it's now controversial to point that out, we've got a serious problem on our hands.
Of course, to reiterate again, Walt & Mearsheimer's thesis is not about who opposes their ideal vision of mid-east policy. It's about their perception that the Israel Lobby possesses extreme control over US foreign policy that leads us to do things their predictive model says shouldn't happen. When we collapse every policy that deviates from the Commentary Magazine line as "subscribing to the Walt-Mearsheimer thesis", we're exploding their argument way beyond its actual scope.