Republican tax lobbyist Charls E. Walker in his office in 1983. (Bill Snead/The Washington Post)

Charls E. Walker, a Republican economist who served as a top Treasury Department official in the Nixon administration and became a prominent and irrepressibly colorful tax lobbyist for some of the biggest American corporations, died June 2 at a nursing center in Rockville, Md. He was 91.

The cause was complications from heart ailments, said a daughter, Carolyn Lee.

Dr. Walker was Texas-born and retained a Texas-size affability and swagger long after relocating to the nation’s capital, where for decades he was among a select and powerful cadre of Washington insiders with access to presidents and congressional leaders.

In his heyday, he was often compared to Thomas H. Boggs Jr., the elite Washington lobbyist and dealmaker, but Dr. Walker was focused on taxes and finance where Boggs, who died in September at 73, worked across a spectrum of policy goals.

In a field that depends on networks and friendships, Dr. Walker was boisterous and jovial. Although aligned with the GOP, he was widely known at the highest levels of power among members of both major parties.

President Lyndon B. Johnson, a friend and fellow Texan, once called him an “s.o.b. with elbows.” but Dr. Walker often explained to reporters, “where I come from, that’s a term of endearment.”

Publicly, he embraced a country boy persona, chomping on cigars, extolling the virtues of bourbon, barbecue and fried catfish. He was a licenced pilot who liked to land his amphibious aircraft on the Potomac River or Possum Kingdom Lake in Texas, where he had a vacation home.

To the self-important and gravely serious participants at tax policy discussions, Dr. Walker delighted in introducing himself by saying, “I’m from Possum Kingdom.” In Washington, Dr. Walker’s talent was for explaining complex legal, taxation and banking issues in terms easily understandable to laymen; he wrote a newsletter that once used a golf analogy to illuminate a point about Keynesian economics.

He also learned early on to curry favor with the media, which he considered an asset far more than an adversary, as the political columnist Jules Witcover once observed.

In a 1975 Washington Post profile, Witcover described Dr. Walker as a “wunderkind,” a Wharton-educated economist who, at 35, was named an assistant to Treasury Secretary Robert B. Anderson at the end of the Eisenhower administration. He left the government for much of the 1960s, when Democrats held the White House, and became a top executive and chief lobbyist for the American Bankers Association.

He returned to federal service in 1969 after Richard M. Nixon’s election victory, and he rose from undersecretary to deputy secretary of the Treasury.

In 1973, Dr. Walker started a lobbying firm that forged close ties to big business, and his clients included General Motors, Gulf Oil, Alcoa and several major airlines — “a few mom-and-pop clients,” he joked. He also started the American Council for Capital Formation, a research and advocacy organization pressing for tax policies favorable to corporate interests.

He benefited not only from his expertise on legislation but his close relations with lawmakers and policy shapers, including fellow economist James R. Schlesinger, who became secretary of defense in the Nixon and Ford administrations and secretary of energy under President Jimmy Carter. He was a godfather to one of Schlesinger’s sons.

Dr. Walker also was on close enough terms with Sen. Russell B. Long (D-La.), chairman of the powerful Committee on Finance, to call him at home with frequency.

Until he retired in the mid-1990s, Dr. Walker had a voice in most, if not all, federal tax policy debates and was said to have been influential in bringing about the capital gains tax cut of 1978 under Carter and in shaping business provisions of President Ronald Reagan’s 1981 tax package, when corporate taxes were substantially reduced.

He did not always prevail. In a 1986 tax bill that effectively raised corporate taxes by eliminating an investment tax credit, “I got my butt beat,” he admitted to the New York Times.

Even political adversaries, including Sen. William Proxmire (D-Wis.), admired his formidable skills, if not his policy views. “He never quite escaped his ABA bias — that banks should continue to call all the shots on credit and related matters,” Proxmire once told The Post. “There hasn’t been one piece of consumer credit legislation that Charly hasn’t led the fight against.”

Charls Edward Walker was born Dec. 24, 1923, in the north-central Texas town of Graham. His mother omitted the letter “e” from his first name because she didn’t want him to be called “Charlie.”

Her gambit was not entirely successful. He was sometimes known as Charls “No E Walker,” and he was widely called “Charly,” spelled differently from “Charlie” but pronounced the same.

He was about 5 when his father died, and his mother turned the family home into a hotel during the Depression; he sometimes had to give up his room to a guest and sleep on the porch.

During World War II, he was an Army Air Forces bomber pilot and flight instructor.

In 1947, he graduated from the University of Texas at Austin, where he also received a master’s degree in business administration. He completed a doctorate in finance at the University of Pennsylvania’s Wharton School in 1955.

Early on, he was an economist with the Federal Reserve Bank of Philadelphia and a vice president and chief economist at the Federal Reserve Bank of Dallas.

Later, at the Treasury, he recalled his brush with history in 1971 when he fired G. Gordon Liddy, a special assistant to the Treasury secretary, for giving speeches opposing a gun-control measure advocated by the department.

“I called him in, and he took it like the trouper he was,” Dr. Walker told The Post.

Soon afterward, Liddy was hired to serve in the White House “Plumbers” unit, which was involved in the Watergate break-in and coverup that led to Nixon’s resignation in 1974.

Survivors include his wife of 65 years, Harmolyn Hart Walker of Rockville; two children, Carolyn Lee of Montgomery Village, Md., and Charls “Chuck” Walker Jr. of Payson, Ariz.; six grandchildren; 13 great-grandchildren; and two great-great-grandchildren.

For all his love of things Texan, Dr. Walker also showed a flair for the trappings of Washington. He frequented the exclusive Burning Tree Club in Bethesda and lunched in the 1970s at the fashionable Sans Souci in Washington, where a salad was reportedly named after him. His preference for chauffeur-driven limousines was often part of the mystique he cultivated.

He also honed a politician’s savvy at delivering a non-answer with a dollop of folksy wit.

Asked for his views on a controversial tax cut during the Ford administration, he told a reporter, “Half my friends think it’s too big, and half my friends think it’s too small. And I never disagree with my friends.”