Louis Harris, 95, the U.S. pollster whose political insights helped steer John F. Kennedy's successful bid for the presidency in 1960 and hundreds of other Democratic campaigns for public office, died Saturday at his home in Key West, Fla., the New York Times reported, citing his grandson Zachary Louis Harris.

The former Navy reservist made his mark on America's political landscape after advising Kennedy on his image and electoral chances against Republican nominee Richard M. Nixon. Mr. Harris' polling persuaded Kennedy to challenge Hubert H. Humphrey for the Democratic primary in West Virginia to prove to the party that a Catholic could win in a Protestant state.

Mr. Harris later coached the Massachusetts senator on how to conduct himself in four televised debates against Nixon that were seen as crucial in deciding the presidential race. Kennedy won a close election with 49.7 percent of the popular vote.

The man who lent his name to the Harris Poll broke with the traditional approaches of George Gallup and Elmo Roper by probing the underlying attitudes of respondents and using the data to advise private clients. While employed by CBS Television in the 1960s, he developed a polling technique that focused on specific precincts whose voting trends could be extrapolated to call election results.

Mr. Harris and his door-knocking employees at New York-based Louis Harris & Associates Inc. used hour-long interviews of ordinary Americans to collate the data that assisted clients such as New York Mayor Robert F. Wagner Jr. and California Governor Edmund G. "Pat" Brown to win their respective races.

The pollster also distinguished himself from competitors after he predicted the outcome of the 1980 election that pitted Ronald Reagan against Jimmy Carter.

In 1956, the young pollster founded Louis Harris & Associates and helped Kennedy on his reelection campaign in Massachusetts two years later.

Mr. Harris replaced Roper as public-opinion analyst at CBS in 1962 and started as a columnist at Newsweek and the Washington Post the following year.