From 1993 to 1997, Dr. Gerrard was a member of Prime Minister Jean Chretien's cabinet as the Secretary of State for Science, Research and Development and from 1996 to 1997 responsible for Western Economic Diversification. In this role he was a leader in advancing internet access for Canadians and a strong advocate for investments in science and research.

Jon was the leader of the Manitoba Liberal Party from 1998 to 2013. During this period he promoted improvements in health care. This included the prevention and treatment of diabetes. He also focused efforts to help children especially to implement Jordan's Principle and to improve child and family services. He introduced and had passed the Apology Act to enable better communication between health care providers and patients in the case of medical errors. He promoted newborn hearing screening, better support for those with cochlear implants and for individuals needing hearing aids. He was also a leader in advancing environmental stewardship in particular improving the health of Lake Winnipeg and addressing climate change.