when the liberal party formed government following the 2015 federal election, new prime minister justin trudeau did not appoint senator cowan as government senate leader. the position was replaced with the representative of the government in the senate and assigned to independent senator peter harder leaving cowan as leader of the independent liberal caucus. cowan stepped down as liberal senate caucus leader on june 15, 2016. he retired from the senate upon reaching the mandatory retirement age of 75 on january 22, 2017.