MONTREAL, Canada – A few days before Canada's October 21 general election, all polls predict that neither Justin Trudeau's Liberal Party nor Andrew Scheer and his Conservatives will get an absolute majority.
If voting intentions pan out as forecast, the next prime minister will have to form alliances with one or more smaller party to survive confidence votes in the House of Commons and keep his minority government in power.
If a party wins an absolute majority
The House of Commons or lower house of parliament has 338 seats. To obtain an absolute majority, a party must obtain at least 170 seats, which usually requires at least 40% of the popular vote.
The Liberals of Justin Trudeau held 177 seats when parliament was dissolved last month for the election.
If a party gets at least 170 seats, its leader becomes prime minister.
If no party wins an absolute majority
In theory, the party with the most seats forms the government, but this is not guaranteed.
"It's not necessarily the party leader who gets the most seats that forms the government," says Francois Rocher, a politics professor at the University of Ottawa.
To govern the country, "by convention a prime minister must ensure that he gets the support of a majority of MPs in the House of Commons." Trudeau remains prime minister until he either resigns or is forced out in a vote of no confidence.
"So Trudeau could get fewer seats than the Conservatives but still decide to stay in power if he thinks he can get the support of the opposition parties when he submits bills."
According to the latest projections, the Trudeau Liberals could win between 130 and 145 seats.
To stay in power, he could then count on the support of the New Democratic Party (NDP), the Green Party, or the separatist Bloc Quebecois, "which complicates things considerably," according to Rocher.
If the Liberals get more than 160 seats, they can try to govern as though they have a majority, as long as they get majority backing in parliamentary votes. "It's all about political skill," says Rocher.
On the other hand, a minority government led by Andrew Scheer would find it more difficult to make alliances in parliament as NDP leader Jagmeet Singh has ruled out propping up a Conservative minority government.
The Bloc and Green Party are firmly opposed to Scheer's plan to roll back environmental policies, notably a carbon tax, introduced by the Liberals.
The Bloc said it would decide whom to back on a parliamentary vote by vote basis, while Green Party leader Elizabeth May declined to comment on possible scenarios, saying she's "keeping her powder dry."
Is a coalition government possible?
In theory, yes, but in practice it's unlikely.
"It's not part of Canadian political culture," according to Rocher. It happened once, in 1917, when Conservatives and Liberals formed a coalition government to pass a conscription bill in the midst of World War I.
When will we know who will be PM?
Monday evening if a party wins a majority.
In the more likely scenario of a minority government, it could take weeks, if not months.
If Trudeau decides to stay in power – whether the Liberals are in the majority or not – he would first form a new government and then develop his legislative agenda, unveiling it in a "Speech from the Throne."
This is delivered by the governor general, the federal viceregal representative of Canada's monarch, Queen Elizabeth II, at the first convening of the new parliament.
Are the polls right?
Probabilities of a majority government are slim but caution is urged. "In 2015, neither experts nor the polls forecast that Justin Trudeau and his Liberals coming from third place to win in a landslide," says Rocher. – Rappler.com