The letter and other documents indicate that Mr. Sargeant currently has just one other partner in the venture, suggesting that they would largely divide those profits. “Mr. Sargeant’s personal gain from these four contracts may have been $70 million or higher,” Mr. Waxman’s letter says.

A spokesman for Mr. Gates, Chris Isleib, said that the Pentagon had supplied all the documents that Mr. Waxman had requested in the case. “As a result of these documents and subsequent discussions with the committee, Congressman Waxman asked the secretary of defense to investigate allegations that I.O.T.C. has overcharged for the delivery of fuel,” Mr. Isleib said in an e-mail message. The Pentagon will respond directly to the committee on that request, Mr. Isleib said.

Image Harry Sargeant III is the finance chairman of the Florida Republican Party. Credit... S.V. Date/Palm Beach Post

Jim Greer, the chairman of the Republican Party of Florida, said, “Since Harry Sargeant has been the finance chairman, he has always demonstrated the highest degree of ethics and integrity and has always served the party well.”

Brian Rogers, a spokesman for the McCain campaign, said: “This obviously has nothing do with the McCain campaign. John McCain has always called for full transparency in military contracting, and if there’s a nonpolitical mechanism for looking at credible allegations, then that should obviously go forward.”

Ryan Alexander, president of Taxpayers for Common Sense in Washington, said that further investigation was warranted even though the initial inquiry did not turn up direct evidence of political meddling. Mr. Waxman estimated that if the lowest bidder had been awarded the contracts, taxpayers would have saved some $180 million.

“The fact that the contracting officer warned them lends credence to the general allegation that this is profiteering and that this is an unfair contract,” Ms. Alexander said. “To allow that high of a profit to deliver fuel to the troops is not the kind of management we need right now.”