Robert Sherrill, a self-described “independent radical” journalist who brought an acerbic, at times polemical, wit to books about political leaders including Lyndon B. Johnson and Edward Kennedy, to topics such as military judicial abuses, and to moneyed interests like Big Oil and the gun industry, died Aug. 19 in Tallahassee. He was 89.

The cause was pneumonia, said his goddaughter, Sidney Brammer. A former Washington resident, Mr. Sherrill moved to Tallahassee in the early 1980s.

Mr. Sherrill — “an inexhaustible loner of Washington journalism,” the journalist William Greider once called him — had a long association with the leftward-leaning magazine the Nation, serving at various times as its Washington editor and White House correspondent.

He also contributed to periodicals such as Playboy, Esquire, the Atlantic Monthly, and newspapers including the New York Times, often writing long-form magazine stories that caused dyspepsia among his targets. He was among the dozens of journalists who appeared on President Richard M. Nixon’s list of political opponents and enemies.

The hallmarks of Mr. Sherrill’s writing, especially in his heyday in the 1960s and 1970s, was his muckraking zeal aimed at the powerful, his ability to elegantly synthesize reams of research, and a talent for shiv-like phrasing.

“He was the progressives’ contrarian writer,” said the consumer advocate Ralph Nader. “He took the shibboleths of liberalism and exposed them as what he felt they were. He took liberals and progressives down a peg or two, or 10 pegs or two.”

He wrote powerfully about hunger and poverty in the United States, about systematic flaws with the death penalty, massive defense budgets in peacetime, and corporate greed. His most memorable barbs were reserved for those who held high public office and fell short of his ideals.

“The Accidental President” (1967) was his one-man assault on President Johnson as “treacherous, dishonest, manic-aggressive, petty, spoiled.” In “The Drugstore Liberal,” written with Harry W. Ernst, Mr. Sherrill offered a lashing critique of Vice President Hubert Humphrey’s political character.

The book, which appeared as Humphrey was seeking the presidential nomination in 1968, charged that the candidate had abandoned his liberal beliefs and that he was willing to compromise on civil rights and the Vietnam War to satisfy his ambitions. The authors called him a “weeping hawk” (referring to his habit of tearing up) and a “pudgy huckster.”

“The Drugstore Liberal” was picked up by Grossman Publishers, a gadfly New York press, after McGraw-Hill dropped a promise to print the book, reportedly because of White House pressure.

In the New York Times, the political writer Patrick Anderson praised Mr. Sherrill’s flair but argued that the book was off-base in “documenting that Humphrey is a shrewd, glib, compromising, fancy-stepping pragmatist — in short, the sort of fellow we usually choose to be our President.”

In 1974, Mr. Sherrill wrote a coolly dispassionate and much-praised Times magazine story about Sen. Edward M. Kennedy (D-Mass.) and the discrepancies in his public statements about the Chappaquiddick incident that trailed him for the rest of his life. The senator drove his car off a bridge on Chappaquiddick Island, Mass., in 1969, an accident that took the life of his young female passenger, Mary Jo Kopechne.

Author and journalist Robert Sherrill in the late 1960s. (Photo by MHS Inc./Grossman Publishers)

The article grew into Mr. Sherrill’s 1976 volume “The Last Kennedy,” which Greider in The Washington Post faulted as a “slander book about Chappaquiddick.”

“It was assembled, he tells us with his usual blunt stroke, in ‘capitalistic haste’ and there is no false modesty there,” Greider wrote. “But ironically, the book is much less effective than the articles it recycles because Sherrill has reverted to his natural polemical style, pushing every evenhanded judgment to the edge of doubt.”

Mr. Sherrill’s other books include “Gothic Politics in the Deep South” (1968), which profiles George Wallace of Alabama and other leaders in what he called “the new Confederacy,” and “The Oil Follies of 1970-1980” (1983), about price gouging and other unsavory practices of the petroleum industry. In 1970, he wrote “Military Justice Is to Justice as Military Music Is to Music,” whose title revived French statesman Georges Clemenceau’s famed quip.

Nader praised Mr. Sherrill for his ability to weave an ebullient narrative from such arid sources as congressional hearings, Justice Department reports, jury verdicts and shareholder exposes. He could be masterful at renovating slang.

In “The Saturday Night Special” (1973), his acclaimed look at gun control, the proliferation of handguns became “a phantasmagoria of roscoes.”

Robert Glenn Sherrill was born on Christmas Eve, 1924, in Frogtown, a community in Georgia that no longer exists. He grew up in the South and Midwest as his father, a hard-drinking itinerant newspaperman, found work.

“The only thing my father taught me,” he later said, “was how to safely catch a moving freight train, and that came in handy a couple of times.”

After service in the Merchant Marine during World War II, he graduated in 1949 from what is now Pepperdine University in Malibu, Calif. He received a master’s degree in English from the University of Texas in 1956, all the while roaming from job to job.

In 1960, he became an associate editor at the Texas Observer, a small-circulation Austin newspaper that made an outsize impact for its investigative prowess. The editor, Willie Morris, later to gain renown as editor in chief of Harper’s Magazine, described Mr. Sherrill in the book “North Toward Home.”

“Sherrill had been around,” Morris wrote. “He had worked as a newspaper carrier, a janitor, a house painter and a water analyst. He was a veteran reporter who had written, in the old tradition, for some 25 papers all over America. When he grew tired of one town, or began to hate an editors’s guts too much for his own sense of balance, he would simply depart for another, usually in the dead of night.”

Mr. Sherrill had a brief stint as a political writer for the Miami Herald. He was proud of articles that exposed racial injustice in executions. But the job foundered after he came to blows with an aide to Florida Gov. C. Farris Bryant while aboard a Johnson campaign train in 1964.

“There wasn’t much to it, I don’t think,” Mr. Sherrill told the Atlanta Weekly decades later. “I may have messed up a guy’s jaw, but it wasn’t a big deal.” (The incident was later used by the Secret Service to deny him a White House press pass for years.)

He settled in Washington in 1965 as a correspondent for the St. Petersburg Times, but he said he was fired for his prolific freelancing.

His first wife, Mary Bergeson, whom he married in 1950 and became his unofficial research assistant and editor, died in 1994. Survivors include his wife of nearly 20 years, Jean Williams Dugger Marshall Sherrill of Tallahassee; two stepchildren; and a granddaughter.

Mr. Sherrill granted no quarter to anyone or anything — even to the Nation, which published about 200 of his articles over the decades. “My salary was zero,” he told the Atlanta Weekly. “I got paid by the piece and precious little at that, but they were generous with their titles, and a title means a lot in Washington, which is such a phony town that it is taken in by such tommyrot.”