Did a Democratic member of Congress improperly enlist the support of a major pro-Israel lobbying group to try to win a top committee assignment? That’s the question at the heart of an ongoing investigation by the FBI and Justice Department prosecutors, who are examining whether Rep. Jane Harman of California and the American Israel Public Affairs Committee (AIPAC) may have violated the law in a scheme to get Harman reappointed as the top Democrat on the House intelligence committee, according to knowledgeable sources in and out of the U.S. government.

The sources tell TIME that the investigation by Justice and the Federal Bureau of Investigation, which has simmered out of sight since about the middle of last year, is examining whether Harman and AIPAC arranged for wealthy supporters to lobby House Democratic leader Nancy Pelosi on Harman’s behalf. Harman said Thursday in a voicemail message that any investigation of — or allegation of improper conduct by — her would be “irresponsible, laughable and scurrilous.” On Friday, Washington GOP super lawyer Ted Olson left voicemail messages underscoring that Harman has no knowledge of any investigation. “Congresswoman Harman has asked me to follow up on calls you’ve had,” Olson said. “She is not aware of any such investigation, does not believe that it is occurring, and wanted to make sure that you and your editors knew that as far as she knows, that’s not true… . No one from the Justice Department has contacted her.” It is not, however, a given that Harman would know that she is under investigation. In a follow-up phone call from California, Olson said Harman hired him this morning because she takes seriously the possibility of a media report about an investigation of her, even though she does not believe it herself.

A spokesman for AIPAC, a powerful Washington-based organization with more than 100,000 members across the U.S., denied any wrongdoing by the group and stressed that it is not taking sides in regards to the committee assignment. Spokespersons for Justice and the FBI declined to comment.

The case is a spin-off of a probe that has already led to charges under the Espionage Act against two AIPAC lobbyists, whose case is still pending, and to a 12-and-a-half-year prison sentence for former Defense Intelligence Agency official Lawrence A. Franklin. Franklin pleaded guilty a year ago to three felony counts involving improper disclosure and handling of classified information about the Middle East and terrorism to the two lobbyists, who in turn are accused of passing it on to a journalist and a foreign government, widely believed to be Israel. The two lobbyists, who have denied any wrongdoing but were dismissed by AIPAC in April of 2005, were indicted on felony counts of conspiring with government officials to receive classified information they were not authorized to have access to and providing national defense information to people not entitled to receive it.

Around mid-2005, the investigation expanded to cover aspects of Harman’s quiet but aggressive campaign to persuade House Minority Leader Nancy Pelosi to reappoint her to the prestigious position on the House intel panel. The alleged campaign to support Harman for the leadership post came amid media reports that Pelosi had soured on her California colleague and might name Rep. Alcee Hastings of Florida, himself a major supporter of Israel, to succeed Harman.

The sources say the probe also involves whether, in exchange for the help from AIPAC, Harman agreed to help try to persuade the Administration to go lighter on the AIPAC officials caught up in the ongoing investigation. If that happened, it might be construed as an illegal quid pro quo, depending on the context of the situation. But the sources caution that there has been no decision to charge anyone and that it is unclear whether Harman and AIPAC acted on the idea.

AIPAC spokesman Patrick Dorton denies that the organization has engaged in any improper conduct. “Both Congressman Hastings and Congresswoman Harman are strong leaders on issues of importance to the pro-Israel community and would be exemplary Democratic leaders for the House intelligence committee,” Dorton said. “AIPAC would never engage in a quid pro quo in relation to a federal investigation or any federal matter and the notion that it would do so is preposterous. AIPAC is not aware that the Justice Department is looking into issues involving the intelligence committee, and has not been asked any questions or contacted by the government on this matter, but certainly would cooperate with any inquiry.” Dorton added that AIPAC has previously been assured that the organization and its current employees are not being investigated.

In this same investigation, the Justice Department has previously suggested that AIPAC had questionable motives in trying to help a valued government contact remain in a sensitive national security post. The Justice Department alleges in its indictment of Franklin that he asked one of the two AIPAC lobbyists to “put in a good word” for him in seeking assignment to the National Security Council. The document says the AIPAC official noted that such a job would put Franklin “by the elbow of the President” and said he would “do what I can.”

AIPAC lists praise from Pelosi among a series of quotes from world leaders on its website: “The special relationship between the United States and Israel is as strong as it is because of your [AIPAC’s] fidelity to that partnership…” But congressional sources say Pelosi has been infuriated by pressure from some major donors lobbying on behalf of Harman. In a story touching on tensions between Pelosi and Harman, an alternative California publication, LA Weekly, reported in May that Harman “had some major contributors call Pelosi to impress upon her the importance of keeping Jane in place. According to these members, this tactic, too, hasn’t endeared Harman to Pelosi.”

A congressional source tells TIME that the lobbbying for Harman has included a phone call several months ago from entertainment industry billionaire and major Democratic party contributor Haim Saban. A Saban spokeswoman said he could not be reached for comment. A phone call pushing for a particular member’s committee assignment might be unwelcome, but it would not normally be illegal on its own. And it is unclear whether Saban — who made much of his fortune with the Mighty Morphin Power Rangers children’s franchise — knew that lobbying Pelosi might be viewed by others as part of a larger alleged plan.

Saban has donated at least $3,000 to Harman’s campaign, according to Federal Election Commission records, and the Saban Center for Middle East Policy, which he sponsors at the prestigious Brookings Institution, boasts Harman among its biggest fans. “When the Saban Center talks, I listen,” Harman said at a Saban Center briefing in February on U.S. strategy in Iraq. Harman quipped that, in order to attend the session at Brookings, she had to “blow off” a senior intelligence official’s appearance before a House committee.

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