John J. Rhodes, 86, an Arizona Republican who as minority leader of the House of Representatives played a critical role in the events leading to the 1974 resignation of President Richard M. Nixon, died of cancer Aug. 24 at his home in Mesa, Ariz.

Two days before Nixon quit the presidency, Mr. Rhodes was one of three influential Republicans who called on him at the White House to tell him in the bluntest terms that his struggle to remain in office was lost.

His Republican support on Capitol Hill had all but evaporated, Nixon was told by Mr. Rhodes, Senate Minority Leader Hugh D. Scott Jr. (Pa.) and Sen. Barry M. Goldwater (Ariz.). It was virtually certain, they said, that the House would vote to impeach him and that the Senate would convict him on charges related to the 1972 break-in at the national Democratic Party headquarters at the Watergate.

That night Nixon told his family and his chief of staff that he would resign. He announced his plans to the nation on national television the next evening and at noon Aug. 9 his resignation became effective.

A friend and long-standing supporter of Nixon, Mr. Rhodes had not decided until Aug. 6 that he would vote to impeach the chief executive. He reached his decision after the release -- by order of the Supreme Court -- of transcripts of tape-recorded White House conversations in which the president tried to get the Central Intelligence Agency to halt an FBI investigation of the Watergate break-in.

“For me, this is a sad day. I admire Richard Nixon, for the many great things he has done for the people of America and the people of the world,” Mr. Rhodes said in announcing his decision. “But the most important aspect of our entire system of government is equal justice under the law, the principle that no person -- whether he be rich or poor, black or white, ordinary citizen or president -- is above the law. Coverup of criminal activity and misuse of federal agencies can neither be condoned nor tolerated. . . . When the roll is called in the House of Representatives, I will vote ‘aye’ on impeachment.”

On Capitol Hill, the announcement by the House leader of the president’s own party was widely interpreted as the coup de grace for the Nixon presidency. By that afternoon, all 10 Republicans on the House Judiciary Committee, who earlier had voted against impeachment, had reconsidered. They would now vote to impeach, they said. House Speaker Thomas P. “Tip” O’Neill Jr. (D-Mass.) predicted that there would be no more than 75 votes against impeachment in the full House of Representatives.

Years later, Mr. Rhodes would say the trip up Pennsylvania Avenue to meet with Nixon at the White House was the most trying ordeal of his 30 years in Congress. “It was a very difficult thing to do,” he said. “But I think [Nixon] felt he needed to get the word directly from us.”

John Jacob Rhodes II was born in Council Grove, Kan. He graduated from Kansas State University and Harvard Law School. During World War II, he was an administrative officer with the Army Air Forces stationed in Arizona. After the war, he settled in Mesa, near Phoenix, where he opened a law practice and founded a loan and insurance business.

He became active in Republican politics and in 1952 ran for the House of Representatives. Never before had Arizona elected a Republican to the House, but Mr. Rhodes was swept into office in the landslide for the Republican presidential candidate, Dwight D. Eisenhower.

His first term was the only one of his 15 in which the Republicans were the majority party in the House. His congressional career included service on the Appropriations Committee, where he developed a specialty in defense appropriations. In 1965, he became chairman of the House Republican Policy Committee, in which his job was to develop conservative alternatives to legislative proposals of a Democratic administration.

In 1964, he helped launch the presidential bid of fellow Arizonan Goldwater. He shared many of Goldwater’s conservative political positions, but for much of his career, he had operated in the shadow of the colorful and outspoken Goldwater, who was better known, both nationally and in Arizona.

Never a backslapper, Mr. Rhodes had a reputation on Capitol Hill as a Republican team player who generally shunned the media spotlight, did his homework and knew how to count votes.

Syndicated columnist George F. Will wrote of him in January of 1974: “God had a congressman in mind when He made John Rhodes. And he is just what the Founding Fathers had in mind when they designed the House of Representatives, the body intended to be closest to the common man.

“Rhodes looks every inch like a House member ought to look. A little shorter than average, perhaps a little heavier than he ought to be, he dresses in business suits that are almost flamboyantly nondescript.

“His name is not a household word, and probably never will be. To his credit, he probably doesn’t mind a bit.”

In 1976, the Almanac of American Politics said of Mr. Rhodes that he “knows how to tiptoe through the political minefields without getting hurt.”

Mr. Rhodes believed in limited government, sound money and a balanced budget. He took a dim view of most of the Great Society programs of President Lyndon B. Johnson’s administration, and he backed a full military effort in waging the war in Vietnam. For the 1969-70 session of Congress, he was voted “Watchdog of the Year” by the National Association of Businessmen.

In 1972, he was chairman of the platform committee at the Republican National Convention in Miami, where Nixon was nominated for a second term. He chaired the 1976 and 1980 GOP national conventions.

He was elected House minority leader in 1973, replacing Gerald R. Ford, whom Nixon had nominated as vice president to replace Spiro T. Agnew. Agnew had resigned after pleading no contest to a charge of income tax fraud.

For seven years, Mr. Rhodes was minority leader, but they were not good years for the Republican Party, which had to live down the Watergate scandal and then, in 1976, lost the White House to Jimmy Carter.

Frustrated by what he perceived as congressional ineffectiveness, Mr. Rhodes wrote a 1976 book, “The Futile System,” in which he argued that reform in Congress “cannot be accomplished by the majority party. . . . The ins have little incentive to change. It is the outs -- the powerless minority -- who have the only real motivation to take a critical look at the system and determine a better way to run things.”

After seven years as minority leader, Mr. Rhodes had planned to step down in 1980. But with Ronald Reagan at the head of the Republican ticket in the November elections that year he decided to run for one more term. If the Republicans gained control of the House, he would be speaker. But they didn’t, and he wasn’t. He retired as minority leader, served out his last two-year term as a representative from Arizona and then ended his congressional career. He was 66.

“I just thought that if I was ever going to do something else, I should get started doing it,” he said.

After leaving Congress, Mr. Rhodes maintained an apartment in Bethesda and also lived in Mesa. He traveled extensively and practiced law in the Washington office of the Richmond-based firm of Hunton & Williams.

In 2002, Mr. Rhodes and former representative Louis Stokes (D-Ohio) became the first recipients of the newly created Congressional Distinguished Service Awards.

Survivors include Mr. Rhodes’s wife of 61 years, Elizabeth Harvey Rhodes; a daughter, Elizabeth; three sons, Tom, Scott and John J. Rhodes III, who served as a Republican in his father’s old House seat from 1986 to 1992; and 12 grandchildren.