States in September 1945, he accompanied General Stratemeyer to Washington, D.C., where he helped design plans to defend the nation against air raids. Following his return to Philadelphia, Clark resumed his political activity and his partnership with Dilworth. He was manager of Dilworth's unsuccessful campaign for Mayor of Philadelphia against Republican incumbent Bernard Samuel in 1947. He then served as chairman of the citizens' committee for President Harry S. Truman in the 1948 election, and as chairman of the Philadelphia chapter of the Americans for Democratic Action from 1948 to 1949. Running as a reform Democrat, Clark was elected city controller in 1949, winning by more than 100,000 votes. Meanwhile, Dilworth was elected city treasurer by a similar margin. Serving from 1950 to 1952, Clark investigated and publicized scandals within the Republican-controlled city government, including the embezzlement of tax money and court funds, imprisonment of the fire marshal, falsification of records, and corruption in the water bureau. Many officials were impeached or indicted as a result, and nine even committed suicide. Mayor of Philadelphia Clark announced his candidacy for mayor of Philadelphia in May 1951. Democratic leaders had wanted Dilworth to run, but Clark released a press statement declaring his "irrevocable decision to run for mayor." Instead, Dilworth successfully ran for District Attorney of Philadelphia. Running on his record as city controller, Clark often used a broom while campaigning as a symbol of his pledge to "sweep out" corruption. His Republican challenger was Daniel A. Poling, a Baptist clergyman and editor of the Christian Herald. Clark was endorsed by several labor unions, Americans for Democratic Action, and The Philadelphia Inquirer. On November 6, 1951, he defeated Poling by 124,700 votes. With his victory, Clark became the first Democrat to be elected mayor of Philadelphia since 1884; as of 2021, no member of another party has since held the office. Clark was inaugurated as the 90th Mayor of Philadelphia on January 7, 1952. He was the first mayor to serve under Philadelphia's Home Rule Charter, which had reorganized city government by merging Philadelphia's city and county offices, establishing a limit of two successive terms for mayor, replacing patronage with a merit system for civil servants, and giving the mayor increased administrative, legislative, and investigative powers. During his administration, he reduced corruption within the Police Department and appointed several African Americans to city jobs. He adopted a $20 million tax increase and