Lewis was elected as the member for Wollondilly representing the Liberal Party in 1957. When the Askin Government came to power in 1965, Lewis was given relatively junior portfolios of Lands and Mines. As lands minister he was responsible for setting up the NSW National Parks & Wildlife Service in 1967. In 1970, he set up the Foundation for National Parks & Wildlife as an independent not-for-profit organisation, in order to be the fundraising arm of the NSW National Parks & Wildlife Service. In 1972, Tourism was added to his ministerial responsibilities when Eric Willis moved to Education.
Premier
Askin announced his resignation late in 1974, and Lewis was chosen as leader over Willis and Justice Minister John Maddison. He was sworn in on as Premier on 3 January 1975. He was elected during an uneasy time for the Liberal government, being engaged in almost daily warfare with the Whitlam Labor Government in Canberra, most notably over the Medibank health care scheme, to which New South Wales was the last state to sign.[5]
The defining moment of the Lewis government was the decision taken by Lewis to break with convention when Whitlam appointed his Attorney-General, Lionel Murphy, a Senator from New South Wales, to the High Court of Australia. In a break with long-standing convention, Lewis refused to appoint a replacement Senator from the same party, instead appointing the 72-year-old Mayor of Albury, Cleaver Bunton. This triggered immediate outrage, not only from the Labor Party but also the executive of the Liberal party.[5]
By the end of 1975, Lewis' image was badly damaged and he soon lost the confidence of his party. Sentiment was growing in favour of replacing him with Sir Eric Willis. At a caucus meeting on 20 January 1976, parliamentary backbencher Neil Pickard called a spill motion, which was carried 22 votes to 11. Lewis opted not to try to regain his post, leaving Willis to take the leadership unopposed. Lewis's term as Premier came to an end on 23 January 1976, his 54th birthday. Lewis was the only non-elected non-Labor premier who did not take the Coalition into an election.[6]
Later life
Lewis served as Willis' Minister for Local Government until May 1976, when the Liberal Government was narrowly defeated by the Labor Party.[4] In opposition Lewis did not hold any position within the Shadow Cabinet and later resigned from Parliament on 7 September 1978, the vacancy becoming one of the justifications for calling the election for 7 October 1978. At the election, his seat fell to the Labor candidate Bill Knott.[5] On his departure from parliament, he was permitted by Queen Elizabeth II, on the Governor's recommendation, to continue to use the title "The Honourable".[7]
He was made an Officer of the Order of Australia on 26 January 2000 "For service to the Parliament of New South Wales, to the environment as the founder of the NSW National Parks & Wildlife Service, and to the community".[8] On 1 January 2001 he was awarded the Centenary Medal.[9]
Apart from these two honours, Lewis had kept himself out of the public spotlight since his retirement from Parliament.