He was a Labor Party member of the New South Wales Legislative Assembly from 1920 to 1922 and 1925 to 1932, representing the electorates of Parramatta (1920–22, 1925–27) and Granville (1927–1932).
In 1912, he became co-proprietor of the Cumberland Times newspaper in Parramatta, a role he held until his election to parliament.
Ely entered state politics at the 1920 election, when he won the last seat in multi-member Parramatta with the preferences of Jack Lang.
[1] The multi-member system was abolished in 1927, and Ely contested and won the recreated seat of Granville.
His career came to an end at the 1932 election, amidst Labor's heavy defeat after Lang was sacked as Premier by Governor Philip Game; one of many Labor MPs to lose their seats, Ely was defeated by United Australia Party candidate Claude Fleck.