At the outbreak of World War II, Blanc rejoined the military, this time as an officer in the United States Army Air Corps.

He won, part of a Democratic wave that swept the city government out of Republican control for the first time in 67 years.

[3] While on city council, Blanc led an investigation into corruption related to construction at Philadelphia International Airport.

[1] Blanc returned to prosecution in 1955 when he won election as District Attorney of Philadelphia, succeeding Richardson Dilworth, who had resigned to run for mayor.

Blanc, who won the Democratic primary unopposed, handily defeated Republican Wilhelm Knauer in the general election that November.