It is the longest election campaign in Canada's history - and it could be one of the closest.

Current Prime Minister Stephen Harper is fighting for a record fourth term in office, but he has been losing support to his main challenger Justin Trudeau - the leader of the Liberal party, and the son of former Prime Minister Pierre Trudeau.

Canada's top satirist Rick Mercer, host of the Rick Mercer Report, has been talking to the BBC's Rajini Vaidyanathan about the election candidates - and his predictions for the outcome.