Answer
Peter Dutton challenged Malcolm Turnbull for leadership in 2018. Dutton was the Minister for Home Affairs at the time and had been a vocal critic of Turnbull's leadership. The challenge came after a period of poor polling for the Turnbull government and a series of high-profile resignations. Turnbull ultimately defeated Dutton in a leadership spill, but the challenge weakened his position and contributed to his eventual downfall.