Charlton became prominent in the trade union movement, and in 1903 was elected to the New South Wales Legislative Assembly for the Labor Party.

Charlton supported the struggle against wage reductions, but the effort failed and, along with many other miners, he moved to the goldfields near Kalgoorlie, Western Australia.

[1] That idea was opposed as being too radical but a compromise was drawn up urging state governments to open and run their own coal mines, while affirming the ultimate desirability of full nationalisation.

In 1909 a coal miners' strike struck New South Wales and Charlton was called upon by the Colliery Employees' Federation to represent it in front of a wage board.

He resigned from state politics and in 1910 Charlton wrested the federal Division of Hunter from the sitting Frank Liddell.

[8] However, Charlton seemed to accept the affirmative result of the referendum and again proved his loyalty to Hughes by defending him when he became the target of caucus criticism.

[11] Tudor died of heart disease on 10 January 1922, and Charlton became the de facto acting leader of the party.

[14] At the 1922 federal election, Charlton offered alternative policies and looked to be favourite until he was hospitalised with illness halfway through the campaign.

Labor still won the most seats as a single party, but Charlton was unable to defeat a strong government coalition.

[1] Because of great losses during World War I, Charlton opposed military training and commitments of Australian forces.

[1][15] Charlton lost the 1925 election, largely due to his stance on industrial relations and continual militant union action which plagued his campaign.

[1] Following retirement from federal politics, Charlton took an interest in local government and became an alderman on the Lambton Council from 1934 to 1938 (before its merger with the City of Newcastle).