One recent poll shows Justin Trudeau and Stephen Harper neck-and-neck in who Canadians think would make the best prime minister. Another poll puts Mr. Trudeau eight points up on Mr. Harper. But these polls are actually not contradictory, and their differences can tell us something about how the two leaders are perceived.
Nanos Research conducts a weekly telephone survey of 250 Canadians, combining responses over a four-week period to obtain a sample of 1,000. Their latest survey was conducted in the four weeks ending Feb. 8, and found 29 per cent of Canadians choosing Mr. Trudeau as the best person to be prime minister, followed by Mr. Harper at 28 per cent. NDP Leader Thomas Mulcair came third with 19 per cent, while Green Party Leader Elizabeth May had 4 per cent support and interim leader of the Bloc Québécois, André Bellavance, had 2 per cent.
Ipsos Reid conducted an online survey of 1,001 Canadians for CTV News between Jan. 31 and Feb. 4. Their poll gave Mr. Trudeau 42 per cent support on who would make the best prime minister, with Mr. Harper registering 34 per cent support and Mr. Mulcair 24 per cent.
As the Ipsos Reid survey was done online, a margin of error is not applicable. The Nanos poll was done through a random telephone survey and has a margin of error of plus or minus 3.1 points, 19 times out of 20.
The results of the Nanos poll are consistent with the numbers the firm has been reporting since the end of November, while Ipsos's poll shows little change from the last time this question was asked in the spring of 2013.
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Why the discrepancy between the two? Is this yet another case of polls showing wildly contradictory results?
There is an important difference in the questions these two polls asked. In the Nanos survey, 18 per cent of respondents did not choose one of the five party leaders, either because they were undecided or felt none of them were up to the task. In the Ipsos survey, all respondents had to choose between the three leaders offered. Being undecided or selecting the Green or Bloc leaders was not an option.
This means that in the Ipsos poll, the 24 per cent of Canadians who had told Nanos they were either unsure or chose Ms. May or Mr. Bellavance had to instead choose one of the three main party leaders (practically speaking, only one of the three will become Prime Minister in 2015). This is the reason the numbers were so different, and this difference tells us something about how these Canadians view the other leaders.
Let's assume that, had Ipsos given respondents the full list of possible options, the results of its poll would have been identical to the Nanos poll. In order to get to the final results for just the Liberal, Conservative and NDP leaders, we need to distribute the 24 per cent of Canadians who did not select them initially.
When this is done, we see that 54 per cent of Canadians who were either undecided or supportive of Ms. May and Mr. Bellavance chose Mr. Trudeau as the best person to be prime minister. Only 25 per cent of them went towards Mr. Harper and 21 per cent selected Mr. Mulcair.
While this would seem to put Mr. Trudeau in an advantageous position, it is a bit of a double-edged sword. It does show that Mr. Trudeau is much more popular than either the Conservative or NDP leaders among less committed voters. In an election campaign, when Canadians are being asked to elect a government, that may play in his favour as swing voters move to the Liberals. Both Mr. Harper and Mr. Mulcair have less scope for growth in this regard.
On the other hand, supporters of the Greens and Bloc Québécois will have the opportunity to cast a ballot for these parties, even if they did not have the opportunity to choose the leaders of these parties in the Ipsos poll. And just how likely are the 18 per cent of respondents in the Nanos survey who were undecided to actually cast a vote? If the Liberals are the overwhelming favourite of non-voters, that does not help them win an election.
When Canadians have to make a choice, they prefer Justin Trudeau over either Stephen Harper or Thomas Mulcair. When they do not have to make a choice, the Liberal and Conservative leaders are neck-and-neck. Accordingly, the impact of turnout for the two parties in the 2015 election will likely be significant.
Éric Grenier writes about politics and polls at ThreeHundredEight.com.
Editor's note: an earlier version of this story misstated the methodology of the Nanos survey. It was conducted by telephone, not online, and so has a margin of error of plus or minus 3.1 points, 19 times out of 20. This version has been corrected.