Canada's political attack ads

From the outside, the world of Canadian political attack ads is bemusing; from the inside it's a vital part of any successful campaign. Misquoting your opponents, lambasting their policies or insulting their hair - it's all in a days work. Ahead of elections in October, Steve Bloomfield sits down with columnist John Doyle, Dr Erin Tolley from the University of Toronto and Sean Kemp, former special adviser in Downing Street for the Liberal Democrats.