Mackay was held by the Labor Party for all but five years from 1915 to 2024. Labor's dominance in the seat began in 1915 when it was won by William Forgan Smith, who served as Premier of Queensland from 1932 to 1942. He retired undefeated in 1942 and was replaced by long-serving backbencher Fred Graham. who held it until his retirement in 1969. Graham was succeeded by Ed Casey, who lost Labor preselection after only one term in 1972. Casey recontested as an independent and won, doing so again in 1975 before being readmitted to the party in 1977. He subsequently served as Labor leader from 1978 to 1982, and later as a minister in the Goss Labor government. He was succeeded upon his retirement by Tim Mulherin, who was comfortably elected six more times, winning with more than 60% of the vote in 2006.
For the better part of a century, Mackay was a safe Labor seat, remaining in Labor hands even at the height of Joh Bjelke-Petersen's popularity. Aside from Casey's stint as an independent, Labor's grip on the seat was only seriously threatened twice before 2012. In 1957, in the aftermath of the Queensland Labor split, Graham was held to only 42 percent of the vote. In 1986, the apex of Bjelke-Petersen's dominance, Casey was reduced to 53 percent of the two-party vote. At the 2012 election it became the most marginal ALP seat with Mulherin winning 50.5% of the two-party preferred vote. Mulherin was elected deputy leader of what remained of Labor; it was reduced to only seven seats.
Mulherin retired in 2015, and the seat reverted to its traditional status as a safe Labor seat, with Julieanne Gilbert retaining the seat for Labor on a swing of 12 percent. She retired in 2012, and the Liberal National Party's Nigel Dalton finally broke the long Labor run in Mackay as his party won government. Dalton took the seat on a swing of over 17 percent, enough to technically make Mackay a safe LNP seat.
