 Blackley started off in politics as an alderman on the Maryborough City Council between 1915 and 1922 and for part of that time he was the city's Mayor.He stood as the Country and Progressive National Party candidate at the 1929 Queensland state election, but was beaten by Labor's David Weir.Weir died three months later and Blackley won the resulting by-election in October of that year, defeating Labor's Kerry Copley.