Theodore J. Lowi, a venerated political scientist who challenged conventional scholarship on presidential power and identified the emergence of what he called “interest-group liberalism,” died on Feb. 17 in Ithaca, N.Y. He was 85.

His death was confirmed by his daughter, Anna Lowi.

Professor Lowi taught at Cornell University from 1959 to 1965, returned in 1972 and remained the John L. Senior professor of American institutions until he was granted emeritus status in 2015.

Coupling academic expertise with charisma, he popularized his theories with an evangelical zeal and a Southern drawl in lectures, television appearances and groundbreaking books, which he was said to have dictated verbatim into a tape recorder.

They included “The End of Liberalism: The Second Republic of the United States” (1969), “The Politics of Disorder” (1971), “American Government: Incomplete Conquest” (1976) and “Hyperpolitics: An Interactive Dictionary of Political Science” (2010), written with Mauro Calise. He also edited “The Pursuit of Justice” (1964), Robert F. Kennedy’s book about his tenure as attorney general.