Frederick Cheney LaRue, 75, the shadowy Nixon White House aide and “bagman” who delivered more than $300,000 in payoffs to Watergate conspirators, died of coronary artery disease in a Biloxi, Miss., motel room, where he lived.

His body was found by a motel maid July 27, but Harrison County, Miss., coroner Gary Hargrove said he believed the death occurred July 24. Mr. LaRue had a history of heart problems, Hargrove said.

Considered one of the most mysterious men in the Nixon administration, Mr. LaRue served as a presidential aide without title, salary or mention in the White House directory. Yet he was so close to the center of power that he was one of the few present at a March 30, 1972, meeting at Nixon’s vacation home on Key Biscayne, Fla., at which former attorney general John Mitchell discussed the planned break-in and bugging of the Democratic National Committee headquarters office in the Watergate building.

The money for the operation came from Nixon’s reelection campaign funds, as did “hush money” paid to the Watergate burglars and their attorneys, Mr. LaRue later testified to the Senate Watergate investigative committee. He was the first administration official to plead guilty to charges in the Watergate coverup and was the last to be sentenced. He pleaded guilty to one count of conspiracy to obstruct justice and was sentenced to one to three years, with all but six months suspended. He served 136 days.

Mr. LaRue came to Washington in 1969 as an experienced political hand and was described in a 1972 Washington Post profile as a squinting, mumbling “Faulknerian character, an insignificant-looking man who . . . passionately sought anonymity throughout his wheeler-dealer days.” He was considered the liaison between Mitchell and Mississippi Sen. James O. Eastland (D), who was chairman of the Senate Judiciary Committee and who supported Nixon’s judicial appointments. Mr. LaRue’s role during Nixon’s 1968 election campaign was to woo Southern voters.

Born in Athens, Tex., Mr. LaRue was nicknamed “Bubba” in his family and graduated from the University of Oklahoma with a bachelor’s degree in geology in 1951. His father, Ike Parsons LaRue, went to jail on crimes involving banking law, and upon his release, struck it rich in the oil and gas business. The son sold one of their Mississippi oil fields for a reported $30 million in 1957, using his family’s newfound wealth to become a political financier. Later that year, Mr. LaRue shot and killed his father in a duck-hunting accident in Canada.

Mr. LaRue became active in state Republican politics and served on the Republican National Committee from 1963 to 1968. He donated to Barry Goldwater’s 1964 presidential campaign and was an early donor to Nixon’s 1968 campaign. He was very close to Mitchell, and after the attorney general resigned in 1972 to become campaign director of the Committee to Re-Elect the President (CREEP), Mr. LaRue went with him.

After the Watergate break-in, Mr. LaRue and another aide, Robert C. Mardian, were put in charge of the coverup, supervising the shredding of documents and destruction of financial records.

Hugh W. Sloan Jr., former treasurer of the CREEP Finance Committee, said under oath that Mr. LaRue and deputy campaign manager Jeb Stuart Magruder told him he might have to commit perjury to protect the Watergate conspiracy. They tried to get him to agree to testify that he gave Watergate burglar G. Gordon Liddy much less than the campaign’s financial records showed.

After Mr. LaRue pleaded guilty and served his sentence in 1973, he returned to Mississippi, where he worked in the family oil and real estate development business, his nephew William T. LaRue said. The family money had dwindled by the early 1970s, after the LaRues lost money in the Castaways, a Las Vegas gambling casino they bought in 1963. Mr. LaRue said in 1971, “I’m no millionaire.”

He was one of many Nixon-era figures rumored over the years to be “Deep Throat,” the undercover source of Washington Post reporters Bob Woodward and Carl Bernstein. Mr. LaRue denied that he was Deep Throat, and Woodward said he will not reveal the source’s name until after Deep Throat dies.

Survivors include his wife, Joyce LaRue of Jackson, Miss.; five children; and several grandchildren.