Daley became chairman of the Central Committee of the Cook County Democratic Party, i.e. boss of the political machine, in 1953. Holding this position along with the mayoralty in later years enhanced Daley's power. A recorded phone conversation which Daley had with President Lyndon Johnson on January 27, 1968, revealed that despite his Irish Catholic background, he also privately had at times tense relations with the Kennedy family and that he declined an offer to vote against President Harry Truman when he was serving as a delegate at the 1948 Democratic National Convention.