At the first Australian federal election in 1901, Cook was elected unopposed as member for Parramatta, a seat which then included the Lithgow area [REF].
When Reid resigned as party leader on 16 November 1908, Cook succeeded him the following day, and agreed to merge the Anti-Socialist Party (the Free Trade Party had been renamed prior to the 1906 federal election) with Alfred Deakin's Protectionists, in an effort to counter Labor's popularity.