"The time is now" was a successful campaign slogan for which US president?

Toward the end of Ronald Reagan's acceptence speech at the Republican Convention he starts four paragraphs with "The time is now." The question does say successful campaign slogan for which US President. Maybe at the time Reagan was quoted about his "the time is now," but it was not an official campaign slogan.

loriferber.com/presidential-memorabilia/ronald-w-reagan/ronald-reagan-the-time-is-now-large-campaign-poster-18-24.html [no longer exists]

Ronald Reagan adopted the title of Eli Mellor's (founder of The Time Is Now Institute) 1979 manuscript "The Time Is Now" as the slogan for his 1980 presidential campaign.