L TO R: Frank Armour, Richard Mellon Scaife and Vice President Spiro T. Agnew at 1970 Republican Fundraising dinner at the Pittsburgh Hilton Hotel. (Harry Coughanour/Pittsburgh Post Gazette)

With generous donations to later candidates such as Richard M. Nixon and Ronald Reagan, Mr. Scaife began building momentum for a conservative Republican resurgence. He also was a guiding force behind the Contract With America initiatives of House Speaker Newt Gingrich (R-Ga.) in the early 1990s, as well as the GOP’s tea party progeny in the 21st century.

Mr. Scaife donated millions to such tea party-friendly groups as FreedomWorks, known for its anti-union campaigns and calls for reducing government regulation of business, privatizing Social Security and establishing English as the official language of the United States.

Throughout a life marked by bouts of alcoholism, two turbulent marriages and estrangement from many in his family, Mr. Scaife was at times an erratic shepherd of his deeply felt political beliefs. Some of his most public causes were rooted in elaborate conspiracy theories.

He was a major underwriter of the American Spectator magazine’s Arkansas Project to find evidence of financial and personal misdeeds by the Clintons in the 1990s. The effort included David Brock’s magazine story containing allegations from four Arkansas state troopers that they helped procure women for then-Gov. Bill Clinton.

Brock said he was suspicious of the troopers’ stories but supported their publication anyway, once telling The Washington Post, “I did what was politically useful. [Clinton] was a Democrat, therefore he was a target.”

Most notably, Mr. Scaife personally hired a freelance writer to try to establish that either President Clinton or then-first lady Hillary Rodham Clinton was instrumental in the death of Deputy White House Counsel Vincent W. Foster Jr. in 1993. Foster, a former law-firm partner of the first lady, was found dead from a gunshot wound to the mouth in Fort Marcy Park in Fairfax County.

Three investigations, including one in 1997 by Independent Counsel Kenneth W. Starr, a luminary in the conservative firmament, ruled the death a suicide.

Mr. Scaife was unpersuaded. In 1998, he told George magazine editor in chief John F. Kennedy Jr. that the Foster death was “the Rosetta stone to the Clinton administration,” referring to the ancient Egyptian stone used to decipher hieroglyphics, and that Bill Clinton “can order people done away with at his will. He’s got the entire federal government behind him.”

He also questioned Starr’s other investigations of Clinton’s activities, including the president’s affair with former White House intern Monica S. Lewinsky. “Four years and $40 million later, we haven’t gotten anything,” he said. “Maybe Ken Starr is a mole working for the Democrats.”

As a strong backer of the legal and political strategies against the Clintons, Mr. Scaife made Time magazine’s list of the 25 most influential Americans in 1997. The magazine called him the “horsepower” behind the “resurgent” right.

He was widely believed to have been among those who Hillary Clinton alleged were at the heart of a “vast right-wing conspiracy” against her husband and the constant attacks on his policies and personal life.

Asked about any such conspiracy, Mr. Scaife responded, “If there is one, I don’t know of it.”

He said at the time that he didn’t harbor any personal animosity against the Clintons and that his philanthropy was not solely directed against political opponents or liberal issues. Unlike many fellow conservatives, for example, he supported public television and radio, giving more than $1 million to the Corporation for Public Broadcasting in the late 1990s.

He also was known to turn on political leaders who disappointed him. After generously supporting Nixon’s two terms in the White House, he became outraged by the Watergate scandal in 1974, and his Tribune-Review newspaper called for the president’s impeachment.

“My country comes first; my party comes second,” he said at the time.

In 2008, the paper endorsed Sen. Hillary Clinton (N.Y.) over Sen. Barack Obama (Ill.) in the Democratic primary for president, although some Democratic strategists speculated it was a canny move to support a weaker candidate against the GOP nominee in the general election.

Richard Mellon Scaife was born in Pittsburgh on July 3, 1932, the son of Alan Scaife, a member of a prominent Pittsburgh family, and the former Sarah Mellon, of the even more prominent Mellon family.

One of his mother’s smaller philanthropic gifts funded a virus research lab in Pittsburgh where Jonas Salk discovered his polio vaccine.

Mr. Scaife graduated in 1950 from the private Deerfield Academy in Massachusetts. He went on to Yale University, where he was expelled in his freshman year after a drunken night in which he rolled a beer keg down a flight of stairs and broke the legs of a classmate, according to Mellon family biographer Burton Hersh.

He transferred to the University of Pittsburgh, where his father chaired the board of trustees, and graduated in 1957 with a degree in English.

With his father’s unexpected death a year later, he inherited nominal positions on corporate boards. But his uncle, R.K. Mellon, retained central control, and the two became estranged.

After his mother’s death in 1965, Mr. Scaife assumed direct control of the foundations and trusts she had created. He began shifting the focus of her foundations away from hospitals, universities and family planning to assorted political causes, and within a decade, the bulk of the money was going to conservative think tanks and activist groups.

Mr. Scaife continued to support on a smaller scale a number of nonpolitical entities in Pennsylvania and elsewhere, including the Pittsburgh Symphony, the National Gallery of Art in Washington, and the Brandywine Conservancy in Chadds Ford, Pa., where paintings by Andrew Wyeth are preserved.

In addition, he helped underwrite a new school of public policy at Pepperdine University in California, a campus with a reputation for political conservatism that is affiliated with the Churches of Christ.

He also acquired media properties in the Pittsburgh area and used them to push his conservative themes.

In 1970, he purchased the Tribune-Review, a newspaper in the town of Greensburg 30 miles southeast of Pittsburgh. He moved it into Pittsburgh in 1992 during a crippling labor dispute involving the city’s two principal daily papers, and it quickly became a competing force.

Renamed the Pittsburgh Tribune-Review, it became the centerpiece of a conglomerate of radio stations and other papers throughout western Pennsylvania. From 1977 to 1989, Mr. Scaife was also an owner of the Sacramento Union newspaper in California.

Mr. Scaife had one sister, Cordelia Scaife May, from whom he grew estranged for many years while she managed her own funds in support of such charities as Planned Parenthood and the National Aviary of Pittsburgh. Shortly before her death in 2005, the two reconciled.

Mr. Scaife’s first marriage, to Frances Gilmore, ended in divorce. In 1991, Mr. Scaife married Margaret “Ritchie” Battle, who helped influence his financial giving patterns and expanded their cultural and social life in Pittsburgh.

The marriage became rocky, culminating in messy public divorce proceedings littered with claims and counterclaims over the couple’s possessions. At one point, Mr. Scaife reportedly planted a sign on his lawn that said, “Wife and dog missing — reward for dog.”

Survivors include two children from his first marriage, Jennie K. Scaife of Palm Beach, Fla., and David N. Scaife of Pittsburgh; and two grandchildren, the Tribune-Review reported.

According to news accounts, close friends said Mr. Scaife struggled with alcoholism for years but credited both of his wives and Scaife foundations aide R. Daniel McMichael with getting him into treatment and on the wagon in the early 1990s.

Associates described Mr. Scaife as viewing the political world as divided sharply between allies and adversaries. The late James R. Whelan, editor of the Sacramento Union when Mr. Scaife was an owner there, once told an interviewer: “If you’re not my friend, you’re my enemy — he lives by that kind of code.”

Valentine is a former staff writer for The Washington Post.