Organizations headed by two of the best-known figures in conservative political circles, Ralph Reed and Grover Norquist, have been subpoenaed by the Senate Indian Affairs Committee in its long-running probe of GOP lobbyist Jack Abramoff.

The committee is planning to hold its next hearing in the investigation in late June. The Mississippi Band of Choctaw Indians, one of Abramoff’s former clients, is expected to be the focus of that hearing, according to sources close to the investigation.

Americans for Tax Reform, for which Norquist serves as president, is refusing to disclose its donor list to the Senate committee, said two officials with the group. Reed’s firm, Century Strategies, is complying with the subpoena. Senate investigators are seeking four years’ worth of records detailing Century Strategies’ business dealings with Abramoff and GOP political consultant Michael Scanlon and entities under their control, said several sources familiar with the issue.

Damon Ansell, chief of staff for ATR, said its donor lists are confidential under federal law, and ATR has refused to provide them to the Indian Affairs Committee, which is chaired by Sen. John McCain (R-Ariz.).

“If [Indian Affairs] want[s] to know whether the Choctaws gave us money, they should ask the Choctaws,” said Ansell. “They should ask people if they have given to us.”

ATR’s communications director, Christopher Butler, said in a statement that the group wants to cooperate with the Indian Affairs Committee but has drawn the line at turning over donor records. “Throughout the ongoing investigation by the Senate Committee on Indian Affairs, Americans for Tax Reform has made a concerted effort to cooperate with the investigation,” said Butler. “However, ATR has also been cognizant of the provisions of federal law which provide that ATR donor information is confidential and we have requested on several occasions the Committee enter into a confidentiality agreement with ATR prior to our furnishing confidential donor and financial information. The Committee has instead issued a subpoena requesting all such information.”

Butler added that ATR would today give “a log of the donor and financial documents which we believe are privileged and confidential pursuant to federal statute” to the Indian Affairs Committee, as well as other unspecified documents, although it will continue to refuse to turn over the donor records themselves. Butler would not say what time period the subpoena covers.

Americans for Tax Reform is a 501(c)(4) lobbying organization, according to its Web site, while the Americans for Tax Reform Foundation is a 501(c)(3) research and education group. It was unclear at press time whether the Senate subpoena covers both organizations; Butler was referring to ATR alone in his statement.

Norquist, who was recently married, was leaving for his honeymoon this week and was not available for comment for this article, according to Ansell.

In a brief interview last week, McCain brushed aside questions about the role Norquist and Reed might play in his next round of hearings, reiterating his past claims that his investigation is focused on the wrongs done to the American Indian tribes who paid tens of millions of dollars for questionable services.

“The only thing we’re focused on is where the money went,” McCain said.

In a move aimed at pre-empting criticism from within his own GOP Conference, McCain told his Senate Republican colleagues more than a month ago that he was not framing the investigation in a way that would produce negative stories about — or ethics investigations of — his fellow lawmakers. This statement, made at one of the weekly GOP lunches, came after a slew of reports by Roll Call, National Journal and The Washington Post, among others, questioning the source of funds used to pay for trips taken by House Majority Leader Tom DeLay (R-Texas) as well as other Republican lawmakers and staffers, jaunts that were arranged by Abramoff and his business associates.

In the period covering 2001 to 2003, Reed, the former executive director of the Christian Coalition, was paid roughly $4.2 million by Abramoff, who was then working for the firm Greenberg Traurig, and Scanlon.

Abramoff and Scanlon, who received more than $80 million from a half-dozen American Indian tribes with casino operations from 2001 to 2004, utilized Reed to help block rival tribes from opening their own casinos by mobilizing Christians to oppose new gambling venues in Texas, Louisiana and Alabama. Reed, who once called gambling “a cancer on the American body politic,” has maintained that he never had any direct financial relationship with any casino operator.

“Ralph Reed and Century Strategies have long been opposed to the expansion of casino gambling,” said Lisa Baron, a spokeswoman for Reed, in an e-mail statement. “Century Strategies was approached about assisting with a broad-based coalition opposed to casino gambling expansion, and we were happy to do so. Our firm recruited coalition partners, raised funds, and mobilized grassroots citizens. Our work was legitimate, lawful, and effective. We helped to close illegal casinos that violated federal and state law.”

Baron added: “Greenberg Traurig also raised funds and recruited coalition members. Although we were aware that Greenberg had tribal clients, we had no direct knowledge of their clients or interests. At no time were we retained by nor did we represent any casino company.”

The Indian Affairs Committee and McCain’s personal office declined to comment on the upcoming hearing or subpoenas that have been issued by the panel in its investigation.

Several calls and e-mails to the Mississippi Choctaws for comment were not returned.

Abramoff’s lawyer, Abbe Lowell, declined to comment.

Abramoff and Scanlon are at the center of dual federal and Senate investigations into their dealings with the Indian tribes. Federal investigators are also looking at Abramoff’s relationship with GOP and Democratic lawmakers, including DeLay. DeLay’s ties to Abramoff, including the role that the lobbyist had in funding several overseas trips taken by the Majority Leader and other lawmakers and aides, have become the focus of a burgeoning scandal on Capitol Hill.

The Mississippi Choctaws, for instance, apparently helped fund a DeLay trip to Britain in 2000 thanks to a $25,000 donation to the National Center for Public Policy Research. At that time, Abramoff was on the board of the conservative organization. The tribe gave more than $1 million to the center overall, according to federal tax records.

The Choctaws were also a major donor to the Capitol Athletic Foundation, a nonprofit controlled by Abramoff.

The relationship between Abramoff, Reed and Norquist goes back to the early 1980s when all three worked together for the College Republicans. When Abramoff, then at the firm Preston Gates Ellis Rouvelas Meeds, began lobbying for the Mississippi Choctaws, he used his ties to Norquist, who had by that time founded ATR, to help block new federal taxes on Indian gambling revenue.

According to The Washington Post, the Choctaws, who have become an economic powerhouse in Mississippi thanks to their casino operations, donated “hundreds of thousands” to ATR, although Norquist has refused to reveal how much the tribe gave to his organization.

CORRECTION:The April 21 article “Reed, Norquist Groups Subpoenaed in Probe” incorrectly reported that Ralph Reed’s firm, Century Strategies, was subpoenaed by the Senate Indian Affairs Committee in its probe of former lobbyist Jack Abramoff. Century Strategies is voluntarily complying with a request for documents from the committee.