The title track to this album became Haggard's third consecutive number one country single, but it was its B-side, "I Started Loving You Again" (the "Today" was added to the title later), that became a standard and his most covered song. In the book Merle Haggard: The Running Kind, David Cantwell discusses the song's impact, noting that between 1968 and 1975 alone "at least sixty recordings of the songs were released. There have been pushing that many again in the decades since, and that's without counting the times it's been performed on television through the years, or during mega-star arena shows and don't-forget-to-tip-your-waitress bar sets, or the just-for-fun semipro and amateur versions YouTube lists into the thousands." Singer Bonnie Owens, Haggard's then-wife and band member, played a crucial role in the song's creation. In the episode of CMT's Inside Fame that was dedicated to Haggard's career, Owens remembers that Merle "thought he was out of love with me and wanted out..." Haggard picks up the story, remembering that they were walking through an airport: "I looked at this woman, and she was gorgeous, an absolutely gorgeous lady, and I said, 'You know what? I think I started lovin' you again today.' And she said, 'Turn that around.' And I said, 'Turn what around?' 'Today I started lovin' you again.' I said, 'That gives you half of it.' A few days later Haggard wrote the song alone in a motel room in Dallas. In the same episode, an emotional Haggard chokes up remembering the first time he played it for her, adding, "Some things are hard to tell."
Stephen Thomas Erlewine of AllMusic admires the "unconventional" covers that Haggard chose to record, but states that "they're all overshadowed by 'I Started Loving You Again,' the timeless ballad Haggard co-wrote with Bonnie Owens that stands as one of his greatest moments. Its presence along with the terrific title track and Haggard & the Strangers' restless but quiet musical exploration make The Legend of Bonnie & Clyde another typically excellent album from Hag, who was on a hell of a hot streak late in the '60s, which this simply continues."