dilworth initially ran for mayor in 1947 against incumbent republican barney samuel. samuel was seeking his second full term in office, after assuming office following the death of robert lamberton in 1941. dilworth was ultimately defeated by over 90,000 votes; however, the election marked the last time, to date, that a republican was elected mayor of philadelphia. in 1949, dilworth was elected city treasurer, while clark was elected city controller. dilworth ran for governor in the 1950 election, losing a close race to john fine. in 1951, he was elected philadelphia district attorney, while clark was elected mayor. clark and dilworth's inaugurations ended a 67-year period of uninterrupted republican control of the city (and instituted a period of uninterrupted democratic control which has persisted past 2017). in 1955, dilworth was elected mayor, defeating thacher longstreth.