American Israel Public Affairs Committee
The American Israel Public Affairs Committee (AIPAC), by its own description and that of many analysts, is among the strongest interest groups in the US. "From a small pro-Israel public affairs boutique in the 1950s, AIPAC has grown into a 100,000-member national grassroots movement described by The New York Times as "the most important organization affecting America's relationship with Israel."  Its motto is "America's Pro-Israel Lobby."
It states that receives no financial assistance from Israel, from any national organization or any foreign group. AIPAC is not a political action committee in the regulatory sense, and does not rate, endorse or contribute to candidates. Because it is a lobby, contributions to AIPAC are not tax deductible.
In the John Mearsheimer and Stephen Walt book, The Israel Lobby and U.S. Foreign Policy, it is considered the heart of the broader State of Israel lobby. Some pro-Israel groups, and members of Israeli governments, have had concerns about its influence, and support of the Likud party line. 
AIPAC criticized the awarding of a Presidential Medal of Freedom, by President Barack Obama, to Mary Robinson, former President of Ireland, and a critic of the State of Israel while on the United Nations Commission on Human Rights (now the UN Human Rights Council and the 2001 World Conference Against Racism in Durban, South Africa. The latter, which she chaired, unquestionably had a great number of verbal attacks on Israel, which she did not stop. According to White House Press Secretary Robert Gibbs, "I think the president is recognizing her for her leadership on women's rights and equal rights. And as I've said before, he doesn't agree with each of her statements, but she's certainly somebody who should be honored." Without judging the specific incident, it is an example of AIPAC protest over criticism of Israel. James Zogby, of the Arab American Institute and the Democratic National Committee. called it "proxy war" on Obama.
Along with the American Peace Network (APN), in August 2006, Brit Tzedek v’Shalom was the first Zionist group to directly challenge legislation strongly supported by AIPAC, focused on restricting aid to the Palestinian Authority. According to the Jewish Telegraph Agency, which reported was "the first time in memory a dovish group went toe-to-toe with" AIPAC. Some House members reported a 3-1 ratio of calls in opposition, JTA reported. APN publicly challenged AIPAC on the facts of the issue.
In May 2009, however, it opposed AIPAC from the left while the Zionist Organization of America attacked AIPAC for supporting a Palestinian state. Brit Tzedek v’Shalom, APN and J Street argued AIPAC had not fully supported Barack Obama's peace initiative. 
On the right wing, it may be challenged by the Emergency Committee for Israel (ECI). ECI board member and neoconservative Irving Kristol said"There are some who say they’re pro-Israel but aren’t really ... then there’s AIPAC, which is a wonderful organization, but one that’s very committed to working with the administration, so they pull some punches publicly. ” Kristol's criticism of working with the Administration reflects other comments that wonder to what extent ECI is concerned with Republican interests.
- About AIPAC, American Israel Public Affairs Committee
- Thomas B. Edsall and Molly Moore (5 September 2004), "Pro-Israel Lobby Has Strong Voice: AIPAC Is Embroiled in Investigation of Pentagon Leaks", Washington Post
- Anne E. Kornblut (August 12, 2009), "Honor for Former Irish President Draws Criticism", Washington Post
- James J. Zogby (19 August 2009), "AIPAC's Proxy War on Obama", Facts and Arts
- Bruce Ticker (August 2006), "OpEd: The Lobbies — AIPAC skirmishes with APN and Brit Tzedek v'Shalom.", Philadelphia Jewish Voice
- Ron Kampeas (7 May 2009), "Sitting between Bibi and Obama, AIPAC criticized by left and right", Jewish Telegraph Agency
- James D. Besser (14 July 2010), "GOP Heavies Launch New Pro-Israel Group: Kristol, Bauer target J Street’s candidate in Pa. Senate race.", Jewish Week