In 1903 Charlton was elected to the New South Wales Legislative Assembly, where he served until 1910, when he transferred to federal politics, winning the seat of Hunter from the Liberals. He served as a backbencher through the Labor government of 1910-13 and 1914-16, being considered reliable but not a candidate for the ministry. In 1916 he opposed Billy Hughes's plans to introduce conscription for World War I and went into opposition.
Under Frank Tudor's leadership, Labor was defeated in the 1917 and 1919 elections. Labor recruited the Premier of Queensland, Thomas Ryan to succeed Tudor as leader, but he died suddenly in August 1921. When Tudor also died in January 1922, Charlton was elected leader, despite his lack of obvious leadership talent. Nevertheless, at the 1922 elections, he succeeded in winning some seats from Hughes's Nationalists.
In 1925, however, there was a wave of industrial unrest in Australia, which the Nationalists, now led by Stanley Bruce, blamed on the newly-formed Communist Party. Bruce sought to link Labor to the Communists and the militant unions, despite Charlton's personal reputation as a moderate Labor leader. Bruce called an election in 1925 and won an increased majority.
In 1928 Charlton stepped down as leader and was replaced by James Scullin. He retired from Parliament at the 1928 election and returned to Newcastle, where he served on the Waratah Municipal Council until his death in 1948. He remains the only federal Labor leader never to have held ministerial office.
| Preceded by: Frank Tudor | Leaders of the Australian Labor Party | Followed by: James Scullin |