Three days after he declared his candidacy for the presidency, the man who would leave a near-mythical imprint on America’s political identity seemed decidedly unsure of his own.

That revelation comes from a recently unearthed audio recording made during a private dinner party that the Massachusetts senator and his wife, Jacqueline, hosted in their Georgetown home on Jan. 5, 1960. The tape was given to the JFK Library and Museum in Dorchester last year and was recently discovered by a Brown University historian.

At the dinner party, the recording reveals, Kennedy said he never dreamed of the presidency when he entered politics as a scrawny candidate for Congress in 1946.

“Never. Never. Never,” the future president insisted. “I thought maybe I’d be governor of Massachusetts one day.”

What was irresistible about the decision to seek the presidency, the Harvard alumnus explained to his three guests, was the excitement and challenge of the race itself — “like playing Yale every Saturday, in a sense” — and his unabashed desire to be at the center of the nation’s momentous decisions.

The guests were Newsweek correspondent James M. Cannon and Washington bureau chief Benjamin Bradlee, who later ran the Washington Post, and his wife, Antionette. Bradlee and Cannon were longtime friends of Kennedy and did not report on the conversation.

Cannon’s family gave the tape to the library, and the content will be featured in next month’s Smithsonian magazine. Bradlee did not return calls Tuesday seeking comment.

Ted Widmer, the Brown University historian, said Tuesday that when he came across the tape in his research, “I was just knocked out by it.”

“I thought it was very visceral and immediate, and quite personal. JFK was one of the most successful politicians of the 20th century but he is candid about his liabilities and his inhibitions,” he said. Widmer also said Kennedy’s explanations for why he was seeking the presidency seem strikingly honest.

At one point in the conversation, for example, Kennedy makes another football analogy.

“Johnny Unitas, he might find it interesting to play in a sandlot team, in front of four people, but he’s playing for the Colts, the best team in the United States, for the world championship,” he said. “I’m not comparing the presidency with that, but I’m just saying that, how could it be more fascinating than to run for president under the obstacles and the hurdles that are before me.”

Kennedy “is interested in being at the center of the machinery of government, the center of the action,” said Widmer, rather than seeking the presidency for the lofty goals he outlined in his campaign to secure the Democratic nomination and ultimately defeat Vice President Richard M. Nixon.

The recording portrays a JFK not so sure of himself as he set out on his historic quest, hoping that the electorate sought a new kind of leader who was not necessarily the back-slapping campaigner like his grandfather, the former congressman and Boston mayor John Fitzgerald.

“I think I personally am the antithesis of a politician as I saw my grandfather who was the politician,” Kennedy said. “What he loved to do was what politicians are expected to do. Now I just think that today. . . . I’d rather read a book on a plane than talk to the fellow next to me, and my grandfather wanted to talk to everybody else. I’d rather go out to dinner.”

He later added: “I had not regarded myself as a political type. My father didn’t, he thought I was hopeless.”

But politics attracted him in part, he said, because the alternatives for someone of his social and academic station were so unappealing.