Macdonald studied at the Glasgow Academy and University of Glasgow before undertaking National Service He joined the Scottish National Party (Scottish National Party), and began working on a farm in Kilearn, in 1956 starting a branch of the Scottish National Party in nearby Balfron.
The following year, he inherited the family farm in Newmilns, and started the Irvine Valley branch of the party. He was elected to the Scottish National Party organisation committee, and in 1961 to its executive. The party also stood him as its candidate at the Glasgow Bridgeton by-election, 1961, its first by-election candidacy in nine years.
This result delighted Macdonald, who sold the farm to become the Scottish National Party"s first full-time national organiser since the early 1950s.
Macdonald proved a very effective organiser, travelling the nation to set up new branches. By the time Macdonald stood down, in 1968, the Scottish National Party had gone from having 140 branches to having 484, and official membership had risen to 120,000.
He subsequently became a vice-president of the party, and remained on the party"s national executive through the 1970s, during which time he ran a dry cleaning business. He also stood unsuccessfully for the Scottish National Party in several elections: Clackmannan and Eastern Stirlingshire in 1970, Hamilton in February and October 1974, when he took 39% of the vote, and Central Ayrshire in 1979.
