He was a son of Progressive Conservative cabinet minister Robert Layton (1925-2002). He was born in Montreal and raised in Hudson, Quebec. He rose to prominence in Toronto municipal politics where he campaigned tirelessly for the needs of ordinary citizens and for environmental issues. Eventually, he became head of the Federation of Canadian Municipalities. In 2003, he was elected leader of the NDP on the first ballot of the convention, and the NDP almost doubled its popular vote in the 2004 election.