Joseph Kennedy was prone to self-dramatization, and when he resigned the Chairmanship he announced that he would never return to public life. But by 1936 Kennedy was back in Washington to serve as an unofficial advisor to FDR, promoting the appointment of William O. Douglas to the SEC chairmanship. Kennedy also backed Roosevelt's reelection campaign, lending his name to the book I'm For Roosevelt .
In 1937 Kennedy became the first Chairman of the United States Maritime Commission. His job was to revitalize America's deteriorating commercial fleet and to broker peace with (and within) the tumultuous maritime unions. Although he did put the Maritime Commission on its feet, Kennedy failed to fulfill either objective. Whatever it took to mollify investment bankers did not work with longshoremen, and Kennedy clung too long to the idea of building up a fleet with private capital.
This mixed record continued after 1938 when Kennedy took the most prestigious and visible job of his career: U.S. ambassador to the Court of St. James in London. At first, Kennedy's brashness brought a breath of fresh air to stuffy old England. But Kennedy stayed too long and events overtook him. While Hitler took over Europe, Kennedy backed appeasement and American isolationism, although Roosevelt understood that America would inevitably fight. In the end, Roosevelt did something that he was famous for doing but had never done to Kennedy--he simply ignored him.
Before this arc of descent Kennedy had already realized important professional and personal goals. In 431 days at the Securities and Exchange Commission, he had reformed America's capital markets and become much more than a businessman. He had also made a name for his family and launched his son, John Fitzgerald Kennedy, toward the pinnacle of American political power. He gave America both the SEC and JFK, and it is worth considering that the former may be his more durable, if less heralded, legacy.
Late in life, when asked what drove his career, Kennedy admitted that "I wanted power. I thought money would give me power and so I made money, only to discover that it was politics--not money--that really gave a man power." (Beschloss, 266)
That was a lesson that the father would teach to his son, but it is telling that Joseph P. Kennedy's greatest achievement came when he worked through politics to save American business--a moment when those two warring Kennedy inclinations were in perfect equipoise.