MPs studying the creation of an independent commission to oversee leaders debates during federal elections were quick to arrive at the most fraught question they could dare attempt to answer: Who should be eligible to appear on the biggest stage of an election campaign?

"What about your thoughts on who should be included in the leaders debates?" Liberal MP Filomena Tassi asked Karina Gould, the minister for democratic institutions, at the House of Commons committee on procedure and House affairs on Tuesday. "Is there a threshold in order to meet a participation requirement?"

"Well, I think that's something I'm hoping the committee would push and pursue," Gould responded, "in terms of what they think is reasonable and what they think is necessary for the robust political landscape that we have here in Canada."

The landscape is indeed relatively robust. There are currently 15 federal parties registered with Elections Canada. Seventeen parties ran multiple candidates in the last federal election.

But putting the leader of each of those parties on stage at the same time would likely not make for a particularly useful or relevant debate. 

So a line must be drawn somewhere.

The fun starts when you try to figure out where to draw that line.

Green leader Elizabeth May, who was initially excluded from the broadcast consortium's leaders debates in 2008, presented Gould with one possible threshold for participation: a seat in the House of Commons. 

Gould said she thought that would be a "reasonable criteria" moving forward, though she later suggested this was just one of her initial thoughts (five per cent of the popular vote, she added, could also be a criteria).

Is one MP enough?

To understand the possible implications of a one-MP rule, consider the case of Strength in Democracy, a short-lived party formed in 2014 by an MP who had quit the Bloc Quebecois caucus and one MP who had left the NDP. In 2015, it fielded 17 candidates, most of them in Quebec.

By a simple single-MP standard, Strength in Democracy would have been entitled to a spot in any official debate (it was not represented at any of the five ad hoc debates in 2015). Conceivably, their inclusion might have also have inspired other independent or dissident MPs to form parties with an eye to getting on the main stage.

Alternatively, the rule could be tweaked to say a party must have one MP who was elected under that party's banner (as opposed to an MP who changed affiliation after being elected).

That would exclude a party like Strength in Democracy in 2015, but would allow for something like the Reform party's situation in 1993 — it had one incumbent MP after Deborah Grey won a by-election under the Reform banner in 1989.

Debating the debates...again5:49

A two-part test

But May's Greens have also proposed a more detailed set of criteria.

For inclusion in a debate, the Greens suggest, a party must meet two of three thresholds: an elected MP in the House of Commons, a candidate running in all or nearly all ridings, and four per cent of the national popular vote in the previous election.

"All or nearly all" would have to be quantified, but, for the sake of argument, let's say a party would have to field candidates in at least 90 per cent of ridings to meet that threshold. 

The Liberals, Conservatives and NDP would have met all three of those criteria in 2015, while the Greens and Bloc Quebecois would have qualified by meeting two of the thresholds. The Greens had an MP and fielded 336 candidates. The Bloc had several MPs and received six per cent of the vote in 2011.

But it is interesting to note how those criteria might have applied to at least one previous election. In 1993, the Reform party and Preston Manning would not have qualified for the debates because the party took just two per cent of the vote in 1988 and it fielded only 207 candidates in 1993 (70 per cent of ridings at the time).

That sort of example could make the case for using current public opinion surveys instead of the previous election results as a criteria. (The commission that oversees American presidential debates, for instance, requires that a candidate average 15 per cent or more in a set of recent surveys.)

One other thing about the Green proposal: the difference between a threshold of four per cent and a threshold of, say, five per cent is potentially very significant.

At four per cent, the Bloc Quebecois would be eligible for official debates in 2019. At five per cent, they would come up short: the party received just 4.7 per cent of the vote in 2015.

A debate for smaller parties?

All of this matters because of the status and exposure that a nationally televised debate provides. Commenting on the broadcast consortium's handling of previous debates, Elizabeth May suggested media outlets were able to decide which parties were the "real" parties and there is no doubt something to that. (Coincidentally or not, the Green party's best result was in 2008, when the broadcast consortium was still in control and May was included.)

It remains to be seen whether the MPs studying the issue — hearings continue on Thursday — will decide to recommend criteria or whether they'll be willing to decide that such things are better left to the independent commission the government is aiming to establish.

But near the end of her appearance, Gould floated a potentially intriguing option (or consolation prize): a separate debate for smaller parties.

A debate featuring the leaders of the Libertarian, Marxist-Leninist, Communist, Christian Heritage, Animal Protection and Rhinoceros parties could at least prove wildly more entertaining than the debate between the "real" parties.

Perhaps the possibility of such a debate would even be enough to convince the Natural Law party to come back.