A long-time member of the Country Party, Nalder stood for the Legislative Assembly
seat of Wagin in the
1947 state elections, and was elected over two other Country Party candidates and one
Labor Party candidate. The electoral district of Wagin was abolished in a redistribution prior to the
1950 state elections, and Nalder successfully contested
Katanning, which had been vacated following the decision of
Arthur Watts, the leader of the party, to move to
Stirling. He would hold Katanning until his retirement in 1974, on occasion being re-elected unopposed. Following Labor's defeat in the
1959 state elections, Nalder was named
Minister for Agriculture in the
Brand–Watts Ministry, a position he held from 2 April 1959 through to 3 March 1971. From 12 April 1962, he was also
Minister for Electricity. Nalder had been elected deputy leader of the Country Party in 1956, replacing
Lindsay Thorn, and on Watts' retirement in February 1962, succeeded him as the party's leader (and deputy premier to
David Brand). He remained a member of cabinet in the reconstituted
Brand–Nalder Ministry until the defeat of the Liberal–Country coalition at the
1971 election, and continued in parliament until the
1974 election. ==Later life==