Who was the first US president to use the telephone during his campaign?

The first U.S. president to use the telephone during his campaign was William McKinley in 1896. He utilized the telephone as a tool for communication and to reach out to voters, marking a significant shift in political campaigning. McKinley's campaign manager, Mark Hanna, recognized the potential of the telephone to enhance their outreach efforts. This innovative approach helped to modernize the way candidates engaged with the electorate.