Louis Harris, the nation’s best-known 20th-century pollster, who refined interpretive polling methods and took the pulse of voters and consumers through four decades of elections, wars, racial troubles and cultural revolutions that ran from tail fins to the internet, died on Saturday at his home in Key West, Fla. He was 95.

His death was confirmed by a grandson, Zachary Louis Harris.

From the 1950s, when he founded Louis Harris & Associates, until he retired in the early 1990s, Mr. Harris with remarkable accuracy forecast the elections of presidents, governors, members of Congress and scores of other public officials. Along the way, he used polls to sharpen their images, change their speech patterns and focus their attention on issues of interest to voters.

He told companies how to market products and services, and conducted polls for industry groups, religious organizations, colleges, unions, banks and government agencies.

He also documented trends in American life, from the women’s movement and the ups and downs of the economy to evolving attitudes about marriage, religion, the arts and countless other matters.