She was especially hard on Lyndon Johnson, who had competed bitterly with her husband for the presidency in 1960 and became vice president through the kind of hard calculation for which the Kennedys became known: Johnson was from Texas and the Democrats needed a Southerner to balance the ticket. Once in office, Johnson's imposing personal style and reluctance to speak up during cabinet meetings alienated the Kennedys. They mocked his accent and his manners, while he resented the Kennedys and other "Harvards" he believed looked down on him. Many top aides left soon after Kennedy was assassinated. Robert Kennedy became a public critic of Johnson's presidency and challenged him for the nomination in 1968.

"Jack said it to me sometimes. He said, 'Oh, God, can you ever imagine what would happen to the country if Lyndon were president?'" she recalled.