 He was elected as the Liberal candidate to the House of Commons of Canada for the Quebec electoral district of Outremont in a by-election on November 30, 1942, called after the MP at the time, Thomas Vien, resigned.He defeated future mayor of Montreal Jean Drapeau who was running for the Bloc Populaire.Later that year, Prime minister Mackenzie King named him Minister of National War Services, a post he kept until he became the first Canadian ambassador to Greece on April 17, 1945, a post he kept until 1949.