Michael Pertschuk, a former chairman of the Federal Trade Commission who played a key role in some of the most significant gains in the consumer protection movement, from tobacco control to auto safety regulation, died Nov. 16 at his home in Santa Fe. He was 89.

He had pneumonia, said his wife, Anna Sofaer.

The son of an immigrant furrier, Mr. Pertschuk grew up on Long Island, graduated from Yale Law School, and came to Washington, D.C., as a young Senate staffer in the early 1960s, just as the modern consumer rights movement began to take shape.

Mr. Pertschuk helped lead the movement, which had activist Ralph Nader as its public face, first behind the scenes on the staff of the Senate Commerce Committee under Chairman Warren G. Magnuson, a Washington Democrat, and later as FTC chairman under President Jimmy Carter.

For decades, Mr. Pertschuk cheered advocates — and rankled industry leaders — with his winning campaign to enshrine and enforce government oversight in the marketplace. “He touched every person in this country,’’ Nader said in an interview, describing Mr. Pertschuk as the most “ferocious consumer advocate on a congressional staff in American history.’’

Mr. Pertschuk joined the staff of the Senate Commerce Committee in 1964 as chief counsel, later assuming the duties of staff director. He was among a coterie of Senate aides, a Washington Post reporter wrote in 1977, who occupied “the top stratum of an invisible network of staff power and influence in the Senate, with impact on the life of every citizen of the United States.’’

Magnuson, who campaigned on the slogan “Keep the big boys honest,’’ focused much of the Commerce Committee's activity on consumer protection legislation. Whether with admiration or resentment, Mr. Pertschuk was sometimes called the “101st senator’’ for his central role in that work.

One of Mr. Pertschuk’s first targets was the tobacco industry. In the mid and late 1960s, he helped draft legislation that required cigarette packages to bear the warning: “Caution: Cigarette Smoking May Be Hazardous to Your Health,’’ as well as legislation that banned cigarette advertising on TV and radio.

“Among other things, I spent a good part of my life making life miserable for the tobacco companies,’’ Mr. Pertschuk would later reflect. “And I'm not sorry about that.’’

Another key target of his work was the auto industry, whose safety lapses Nader had exposed in his 1965 book “Unsafe at Any Speed: The Designed-In Dangers of the American Automobile.’’ (Mr. Pertschuk and Nader collaborated so intensely that when Nader attended a birthday celebration for Mr. Pertschuk, Mr. Pertschuk’s then-wife made Nader promise to stop phoning their house after 10 p.m.)

Over forceful lobbying by automakers, Mr. Pertschuk helped win passage in 1966 of the National Traffic and Motor Vehicle Safety Act, which established safety standards for the manufacture of cars.

“The number of lives that have been saved as a result of that law are incredible — millions and millions of lives,’’ said Joan Claybrook, who served under Carter as head of the National Highway Traffic Safety Administration, an agency created by legislation also spearheaded by Mr. Pertschuk.

Mr. Pertschuk was credited with helping to enact the Consumer Product Safety Act of 1972, which established the Consumer Product Safety Commission, and the Magnuson-Moss Act of 1975 governing warranties on consumer products.

His powerful role on the committee at times generated criticism from the Republican minority, which had traditionally defended business interests against what they regarded as government overreach. But it also helped bring him to the attention of President Carter, who named him to chair the FTC in 1977.

The FTC, once dismissed as the “old lady of Pennsylvania Avenue,’’ had already begun under previous chairmen to take a more aggressive approach to oversight. But Mr. Pertschuk took an even more muscular stance, setting out, he said, to make the agency “the best public interest law firm in the country.’’

In Washington’s sea of conservative suits, Mr. Pertschuk stood out in his turtleneck sweaters, the newsletter FTCWatch noted in a retrospective article on Mr. Pertschuk’s tenure. Although armed with Ivy League credentials that might have guaranteed him a perch at a white-shoe law firm, he pledged that he would not appear before the commission if he entered legal practice after leaving government.

“He is not determined to make money,’’ the newsletter noted when he was in office. “He is determined to make change.’’

Mr. Pertschuk continued battling the tobacco industry, in particular its effort to market cigarettes to children.

“Probably nobody had a greater impact on generating the movement that has reduced tobacco use in the United States than Mike Pertschuk,’’ said Matthew L. Myers, a lawyer who investigated tobacco marketing under Mr. Pertschuk at the FTC and is today president of the advocacy group Campaign for Tobacco-Free Kids, which Mr. Pertschuk helped create.

But as Mr. Pertschuk began aiming the FTC’s regulatory power across other industries, from the medical profession to accounting, he began to face anti-regulatory head winds. “He quickly became white-hatted hero to the consumer movement,’’ political scientist Norman J. Ornstein once wrote, and black-hatted villain to conservatives and the business community.’’

The discontent culminated in 1978 with the proposal of the “kidvid’’ rule — later abandoned — which would have prohibited certain TV commercials that marketed sugary foods to children. A Washington Post editorial denounced the measure as “a preposterous intervention that would turn the agency into a great national nanny.’’

Mr. Pertschuk stepped down as FTC chairman in 1981 after President Ronald Reagan, a Republican, unseated Carter. Mr. Pertschuk remained on the commission until 1984 as a vocal member of the minority.

Michael Pertschuk was born in London on Jan. 12, 1933. His father traveled across Europe in the fur trade, the family's business for several generations, and his mother was a homemaker.

Both parents were Jews who left Europe after the rise of Nazism in Germany. They settled in New York in 1937, opening a fur store in Manhattan.

Mr. Pertschuk graduated from Yale University in 1954 and, after two years in the Army, received his law degree in 1959.

His first job in Washington was as a legislative assistant to US Senator Maurine B. Neuberger, an Oregon Democrat. While on her staff, he assisted with committee legwork that led to the official warning by Surgeon General Luther L. Terry in 1964 linking smoking to cancer and heart disease.

Mr. Pertschuk's marriage to Carleen Dooley ended in divorce. In addition to his wife of 45 years, of Santa Fe, survivors include two children from his first marriage, Amy Pertschuk of Sausalito, Calif., and Mark Pertschuk of Berkeley, Calif.; a stepson, Daniel Sofaer of Brooklyn; and three grandchildren.

Mr. Pertschuk wrote several books, including “Smoke in Their Eyes: Lessons in Movement Leadership From the Tobacco Wars’’ (2001) and “When the Senate Worked for Us: The Invisible Role of Staffers in Countering Corporate Lobbies’’ (2017).