The question of who should participate in leaders debates, both federally and provincially, has been a source of a bit of contention lately. Federally, broadcasters have denied Green Party leader Elizabeth May a part in the debate, and provincially Premier Brad Wall has wondered if there should be separate debates between the two parties in the legislature, and another between everyone else. Wall's argument is that last time around, provincial Liberal leader David Karwacki was mostly a distraction.
The question of who should be in the debate is based on what purpose the leader's debate serves. Ideally, it's meant to give voters an idea about what the leaders of all the major parties are all about, and give better insight into the parties they will be voting for. On a local level, any debates should be focused around any candidate running in the riding, since they are all potentially able to get votes. When you get to a larger stage, however, things begin to change.
Personally, I am of the idea that leaders should be included if their party runs in all ridings. This gets complicated on a federal level, since while the Bloc Quebecois has enough seats and influence to matter federally, they still only run in one province. It's difficult to exclude them as a result, especially given that the reaction in their one province would not be favorable, and the pressure on broadcasters who run the debate would be insurmountable. I'd love it if the Bloc was forced to run in every riding, it could give them some much needed perspective on the rest of Canada, but I know that won't happen.
Getting around that somewhat aggravating exception, allowing parties who run candidates everywhere is a way to separate the serious parties from those who are just running on one issue, or can't get much more than very slight support. The level of organization needed to run a comprehensive campaign is such that a party able to manage it will be a party serious about running a campaign.
One issue parties often can't gain the support for a full campaign, and have to develop a complete platform to get more than a handful of people on board. Given the sheer variety of people and areas in the country, one issue parties will often be kept out of some ridings where their issue is controversial or merely not something people care about. Parties which cannot gain popular support are not going to be of interest in a major debate, but are also not going to run all candidates.
Plus, we need to get back to the purpose of the debates themselves, which is to give all residents a chance to get a sense of the parties for which they can vote. Since the goal is to reach everyone, the parties should be available for everyone. I have no interest in a party leader whose party I cannot vote for in a debate, for just that reason. Even if I were to agree with them, it would be irrelevant, because there's not a chance of voting for them.
The debates are for the people, not the leaders, and as a result should only be open to the leaders who can reach all the people. If they cannot inspire enough support to launch a full campaign, they are not going to have enough support to gain a seat, let alone form a government. They have already proven people do not want to hear them.