Today, Canada's 43rd general election officially begins! And tomorrow, you get to hear from the people who want to be your Prime Minister. Well, not all of them, actually. When the first leaders debate of the campaign begins tomorrow night, Justin Trudeau will not be on the stage. Why isn’t he there? Depends on who you ask. But it’s not the only debate the Prime Minister will miss. And that’s certainly a change from the last election. What's different? Well, there's a debate commission now, and there are "official" and "unofficial" debates. And Liberal strategies have changed, too. Winning will do that for you. But Trudeau's absence aside, what will this debate tell us about Oct. 21? Plenty... GUEST: Cormac Mac Sweeney, Parliament Hill reporter