[1][2] In the by-election that resulted from the death of Robert Howe in 1915, Mahony was elected unopposed to the Australian House of Representatives as the Labor member for Dalley.

[3] Following his resignation, he purchased a sub-lease of the Commercial Hotel at Balmain East in June 1927, but sold it again in November.

[7][8] Mahony had emphatically denied the allegations, and claimed that he had won the money gambling on horse-racing.

[5] He attempted to make a comeback at the 1928 federal election, but was defeated for Labor preselection to contest a New South Wales seat in the Australian Senate.

[9][10] In 1929, Mahony was working as a casual assistant in the ambulance room at the Cockatoo Island Dockyard.