Blanchet was born in Drummondville, Quebec, the son of Pierrette Bédard, a nurse, and Raymond Blanchet, a technician and lineman. He is a graduate from the Université de Montréal where he obtained a bachelor's degree in history and anthropology in 1987. He later worked as a teacher and was a founder of an artist, disc and concert management firm, YFB Inc. while being the president of the ADISQ from 2003 to 2006. He was named the local business personality of the year by the DrummondvilleChamber of Commerce, while he and associated artists received 10 Félix Awards. Blanchet was elected to represent the riding of Drummond in the National Assembly of Quebec in the 2008 provincial election. In the 2012 election, he was reelected, this time in Johnsonelectoral district. He was defeated by Coalition Avenir Québec candidate André Lamontagne in the 2014 Quebec election. A member of the Parti Québécois, Blanchet was Minister of Sustainable Development, Environment, Wildlife and Parks from 2012 until 2014. He was also a member of the Youth National Committee of the Parti Québécois in 1988 as well as a regional director of the PQ. On November 26, 2018, Blanchet announced his candidacy for the leadership of the Bloc Québécois. As no other candidate had entered the race by the time nominations closed on January 15, 2019, Blanchet was officially acclaimed leader on January 17, 2019. In the 2019 election, the Bloc polling number rose to his alignment towards the popular Francois Legault's CAQ government. S.E Fortin in the Journal de Montreal noted an article from Don Braid from the Calgary Herald when arguing that people from the prairies province were more worried about Blanchet than environmentalists Dominic Champagne or Steven Guilbeault. He won his seat of Beloeil—Chambly. Under Blanchet's leadership, the BQ increased its number of seats from 10 in 2015, to 32 seats in 2019, both over taking the NDP to become the third largest party in Canada and regaining official party status.
On July 14, 2020, allegations by an anonymous woman were posted on Twitter describing that she was a victim of sexual assault by Blanchet at a Montreal bar in 1999. Blanchet denied the allegations.
