What's a safe lead in the polls? History suggests Trudeau's lead isn't enough

The Liberals are leading in the polls and heading up a minority government that is fast approaching the end of its normal lifespan. This has fuelled speculation that they will try to cash-in on their strong poll numbers with a snap election.

But if waiting until the light at the end of the pandemic tunnel gets a little brighter isn't argument enough to hold off on drawing up the writs, the size of the Liberal lead should make Prime Minister Justin Trudeau think twice.

According to the Canada Poll Tracker, an aggregation of all publicly available polling data, the Liberals hold a national lead of 5.5 percentage points over the Conservatives. That's a solid advantage any party would be happy to take into election day.

Historically, however, it isn't wide enough for a party to be confident of victory before a campaign has even started.

It isn't even that big to begin with.

Since the 1945 federal election, the party ahead in polls conducted 30 to 60 days before an election was held, has averaged a lead of 11 percentage points over the second-place party. Trudeau's lead over Erin O'Toole's Conservatives is only about half that.

Sifting through the historical record suggests that a party ahead in the polls a month or two before voting day should want to have a lead of more than nine percentage points to be reasonably confident of winning. Parties with a lead at least that big have won the most seats in 13 of 14 elections.

The lone exception to the rule was Louis St-Laurent's election bid in 1957. A pre-election Gallup poll had his Liberals ahead of the Progressive Conservatives by 15 points. By election day, the gap had narrowed to just two points and John Diefenbaker's party eked out a narrow minority win.

In the 10 elections where the leading party was ahead by nine points or less, that party only won four times. Those winners were the Liberals under Mackenzie King in 1945, Pierre Trudeau in 1974 and Jean Chrétien in 1993, along with Brian Mulroney and the PCs in 1988.

It's notable, however, that half of the losing parties were those that were in opposition rather than government, including both Tom Mulcair's New Democrats in 2015 and Andrew Scheer's Conservatives in 2019, and that in two cases the losing party nevertheless won the popular vote (the Liberals in 1979 and the Conservatives in 2019).

Campaign swings can be dramatic

The reason why parties can't count on holding a lead in the polls over a five or six week campaign is that public opinion in Canadian elections can swing dramatically.

In 1993, for example, there was a net swing of 22 points between Chrétien's Liberals and the PCs under incumbent prime minister Kim Campbell between pre-election polls and the final results. It was enough to drop the PCs to just two seats and behind the Reform Party in the popular vote.

While that only increased Chrétien's lead, the swing can go just as badly for the party that is ahead.

Double-digit swings against the leading Liberals occurred in 1957, 1965, 1984, 1988 and 2006, as well as against the NDP in 2015.

On average, there has been a swing of three points against the party leading in the polls between the pre-election period and election day. Governments have fared a little better with a net swing of 2.5 points against them, but have still tended to lose support over the course of a campaign.

That is what makes today's Liberal lead in the polls less comfortable than it looks. If we take that 5.5-point lead and swing it uniformly across the country by three points towards the Conservatives, it has a big impact on the Poll Tracker's projection. The Liberals' chances of securing a majority would fall from 48 per cent to 32 per cent, while the chances of a Conservative victory would increase from nine to 19 per cent.

National lead masks regional advantages

Recent history, however, has certainly favoured incumbent governments. Early election calls did not prevent the PCs in New Brunswick or the NDP in British Columbia from winning majority governments. A pandemic election didn't put a dent in the Saskatchewan Party's dominance of their province.

The Liberals in Newfoundland and Labrador, according to the only poll so far released in that province's campaign, appear on track for a landslide victory.

But all those parties had huge leads in the last polls conducted before their elections were called: 18 points for the New Brunswick PCs, 19 points for the B.C. NDP, 32 points for the Saskatchewan Party and 43 points for the N.L. Liberals.

Still, the federal Liberals' national lead masks a significant regional advantage.

According to the Poll Tracker, the Liberals are ahead of the Conservatives by 11 points in Ontario. They are also ahead of the Conservatives by 20 points in Atlantic Canada and hold a seven-point lead over the Bloc Québécois in Quebec. Those are all wider margins than in the 2019 federal election.

Combined with topping the polls in a close three-way race in British Columbia and modest gains in support from the last election in Alberta and Manitoba, this puts the Liberals in a stronger position than their 5.5-point national lead seems to suggest.

Justin Trudeau's own personal ratings remain higher than they were at the end of the last election and are significantly better than O'Toole's, which have taken a downturn in a few recent polls.

Pandemic uncertainty

But then there is the pandemic. There are signs that public opinion is souring somewhat on Trudeau's handling of it, particularly on the question of vaccine procurement.

A survey conducted by Léger for the Association for Canadian Studies has found satisfaction with the measures put in place by the federal government to fight COVID-19 dropping to 54 per cent, the lowest it has been since the beginning of the pandemic.

Another poll by the Angus Reid Institute found the proportion of Canadians surveyed who say the government has done a poor job securing vaccine doses has increased to 44 per cent from 23 per cent in mid-December.

If these numbers are a pre-cursor to a negative trend in the polls against the Liberals, talk about a snap election might get a little more muted — unless, of course, it emboldens the opposition parties into bringing down the government themselves.

But even if the Liberal lead in the polls continues to hold at around five or six points, as it has for most of the last five months, history suggests calling a snap election would be far from a safe bet.