In childish scrawl, and with poor spelling, the author claimed to have met Muskie and his staff in Florida. The author alleges to have asked Muskie how he could understand the problems of African Americans, given Maine's small black population. According to the letter, a member of Muskie's staff then responded, "Not blacks, but we have Canucks" — which the letter spells "Cannocks" — and Muskie laughed at the remark.
On the night of March 4, the Saturday before the March 7 primary, Muskie delivered a speech in front of the offices of the Union Leader, calling its publisher, William Loeb, a liar and lambasting him for impugning the character of Muskie's wife, Jane. Newspapers reported that Muskie cried openly: David Broder of the Washington Post had it that Muskie "broke down three times in as many minutes,"; David Nyhan of the Boston Globe had Muskie "weeping silently." The CBS Evening News showed Muskie's face contorted with emotion. Muskie maintained that if his voice cracked, it cracked from anger; Muskie's antagonist was the same editor who referred to him in the 1968 election as "Moscow Muskie," and called him a flip-flopper. The tears, Muskie claimed, were actually snow melting on his face. Jim Naughton of The New York Times, standing immediately at Muskie's feet, could not confirm that Muskie cried.
Washington Post staff writer Marilyn Berger reported that Nixon White House staffer Ken Clawson had bragged to her about authoring the letter. Clawson denied Berger's account. In October 1972, FBI investigators asserted that the Canuck Letter was part of the dirty tricks campaign against Democrats orchestrated by the Committee to Re-elect the President (CREEP). Loeb, the publisher of the Manchester Union Leader, maintained that the letter was not a fabrication. Loeb later admitted of some doubt, however, after receiving another letter claiming that someone had been paid $1,000 to write the Canuck Letter. The purported author, Paul Morrison of Deerfield Beach, Florida, was never found.
The authorship of the letter is covered at length, in the book and the film, All the President's Men.