Studying law, he was called to the bar in 1880, and in 1883 was appointed Crown Solicitor and Public Prosecutor (the equivalent of solicitor-general).

In 1890, Leake was elected unopposed to the Legislative Assembly (representing the seat of Roebourne), but he resigned shortly after in order to continue as Crown Solicitor.

An opponent of the government of John Forrest, he began to be regarded as the Leader of the Opposition, although that position was unofficial at the time.

Forrest eventually resigned as premier in 1901 to enter federal politics, and was initially replaced by George Throssell.

Alf Morgans was appointed as his successor, but was unable to form a government, resulting in Leake being recommissioned as premier after just a month out of office.

In September 1886, Leake was appointed acting Attorney-General, and was subsequently nominated to the colony's Legislative Council.

On 23 June 1894, Leake was elected as Legislative Assembly member for Albany, and in the following year became Leader of the Opposition.

In 1897 he was chosen as a Western Australian delegate to the Federal Convention, and attended meetings in Adelaide, Sydney and Melbourne.

Morgans then resigned and Leake returned as Premier and Attorney-General on 23 December 1901, this time with much clearer support.