Justin Trudeau's Liberals drop in polls, but is Harper catching up?

Have the Conservatives really caught up to the Liberals in national voting intentions, as one recent poll asserts?

While the margin between the two parties has certainly narrowed in recent weeks, it does not seem to be the case that the Conservatives are the ones on the move.

Stephen Harper's party is currently polling at around 31 per cent support, according to a weighted average of recent polls. That is exactly where the party stood when MPs returned to Ottawa after the summer break in mid-September. 

In fact, the polls have been remarkably steady for the Conservatives over the last few months. Two pollsters that have reported regularly over that time and employed the same methodology throughout have demonstrated this. The Conservatives have managed between 32 and 34 per cent support over the last four surveys by Forum Research going back to August. Abacus Data has pegged Conservative support to be an unflinching 29 to 30 per cent in its four surveys since the summer.

In 28 polls conducted over the last seven months, the Conservatives have averaged 30 per cent, with more than two-thirds of those polls not wavering from that number by more than two points in either direction.

Certainly, the Conservatives are in a better position than they were earlier this year, when most polls put them under the 30 per cent mark. But the race is now more competitive because it is the Liberal Party under Justin Trudeau that has taken a step backwards.

The Liberals are currently averaging about 35 per cent support, down three points from where they stood in September. The party has put up numbers between 32 and 36 per cent over the last six national polls, compared to a range of between 36 and 39 per cent in the previous six surveys. After a strong summer, the Liberals appear to be back to where they were in the first half of 2014. They still lead the Tories, but that margin has decreased by almost half.

Tom Mulcair's New Democrats remain in third place at around 21 per cent support, generally where they have been since the end of the spring.

Instead, the Greens have taken up the slack created by the Liberal slump, putting up between six and 10 per cent support over the last six polls. By comparison, the party had averaged five per cent in all prior surveys conducted in 2014. But is this a real movement towards the Greens, or a statistical fluke?

Finding trends where there are none

So why did a headline in the Toronto Star over the weekend read "Conservatives catch up to Liberals in latest poll," suggesting that the "Tories have closed a large gap"?

The poll in question was produced by Forum Research, and said as much in its own report's headline. But this was an example of a poll being presented in a way that could not be backed up by its own numbers.

In fact, the Conservatives had registered 34 per cent in Forum's previous two surveys, meaning the party had actually dropped one point. By suggesting that it was the Conservatives that had caught up to the Liberals, the implication was that the Tories were the ones with some momentum. But that interpretation does not reflect what was actually going on.

Instead, the Liberals had dropped two points from the previous survey by Forum. While that shift was within the margin of error, and so not statistically significant, the Liberals had consistently fallen from poll to poll by eight points going back to July. 

There's the story to be told, of a gap that has narrowed, or of a drop in Liberal support. But the idea that the Conservatives have "caught up" to the Liberals misses the mark. The Liberals are the ones with the momentum — only negatively so.

ThreeHundredEight.com's polling averages include all publicly released polls, weighing them by sample size, date, and the track record of the polling firm. See here to read more about ThreeHundredEight.com's methodology. The methodology, sample size, and margin of error, if one can be stated, vary from survey to survey and have not been individually verified by the CBC.