Career
Born in Castlemilk, Glasgow, his family moved to Govan at the age of 5, as his father was a caretaker at a local primary school. He left Govan High School at 18, and worked in a variety of jobs including as a retail manager and a holiday representative in Tenerife before becoming a parliamentary case worker for Anne McLaughlin Managing Successful Programmes. After the 2011 Scottish Parliament Elections, he became a case worker for James Dornan Managing Successful Programmes. Stewart was selected unopposed as the Scottish National Party candidate for the Glasgow South constituency in October 2014. In the 2015 United Kingdom Parliamentary Election, McDonald was elected with 54.9% of the vote, defeating the Labour incumbent Tom Harris.
His total represented the largest number of actual Scottish National Party votes in the city, and the largest majority.
McDonald is gay and, on 19 May 2015, gathered with other LGBT Scottish National Party MPs to campaign for a Yes vote in the Irish referendum on same-sex marriage, being held 3 days later.