Depending on the poll you're reading about, the Liberals are either holding a comfortable lead over the Conservatives or locked in a tight race, hobbled by the attacks of new Conservative Leader Andrew Scheer over the government's proposed tax changes.

Either narrative could very well be true — or reality could fit somewhere in between, as it often does. But individual polls considered in isolation only tell a small part of the story.

On the whole, the data suggests the popularity of Justin Trudeau's Liberals has taken a hit. They now sit at 37.6 per cent in the CBC's Poll Tracker, an aggregation of all publicly available polling data. That is a recent low for the party.

The party's lead over the Conservatives is now estimated to be 4.8 points, with the Tories averaging 32.8 per cent. The New Democrats, based solely on polls conducted before Jagmeet Singh became their new leader, sit at 15.8 per cent.

But a few recent polls have shown a much more competitive race and have accordingly garnered some attention.

A statistical tie?

The most recent one, conducted by EKOS Research for The Canadian Press, awarded the Liberals 34 per cent support to 33 per cent for the Conservatives — perhaps an indication the debate over proposed changes to the tax system has cost the government dearly.

But the numbers actually show little movement in voting intentions over the summer months. EKOS last polled in June. Since then, the polling firm found Liberal support inching down 0.9 points, with the Conservatives up 0.3 points. Both shifts are statistically insignificant.

The narrow gap is at odds with most other polls, as it was in June when EKOS gave the Liberals a 2.3-point lead. Other polls conducted at the time gave the Liberals an average lead of nearly seven points.

The EKOS poll also differs from other surveys in the high scores for the Greens and minor parties not represented in the House of Commons. Combined, they had 13.4 per cent support.

But all other polls conducted in 2017 have pegged that combined support to be just 6.7 per cent. That means EKOS sees nearly seven more points for the Greens and minor parties than other pollsters, taking that support off the table for the larger parties and affecting the overall results.

A Conservative lead?

Another poll, conducted by Forum Research, had tongues wagging when it showed the Conservatives moving into a four-point lead over the Liberals — the first poll to show the Liberals behind since the spring.

That previous poll was also conducted by Forum. The Conservatives averaged 35.5 per cent in polls conducted by Forum in 2017 before the firm's latest release. In polls taken by other pollsters over that period, the Conservatives averaged 30.8 per cent.

Several recent polls suggest Conservative Leader Andrew Scheer's attacks on the government's proposed changes to the tax system could be hurting the Liberals. (John Woods/Canadian Press)

Being the pollster that has awarded the Conservatives more support than others is not necessarily a bad thing — the party has often been underestimated in polls compared to its election results — but it does signal that some of Forum's methodological choices are contributing to this difference.

If that support is real, it's not particularly deep. The same poll showed 44 per cent of Canadians didn't have an opinion of Scheer while they preferred Trudeau as prime minister by a margin of 14 points.

Additionally, Forum has tended to show greater variation from poll to poll than other pollsters. In half of Forum's polls this year, Conservative support has oscillated by three or four points. Coupled with the higher support for the Conservatives, this makes it unsurprising that it was a Forum poll that showed a jump for the Conservatives large enough to put them ahead of the Liberals. But it argues against the landscape having actually shifted so dramatically.

Questions matter

An Angus Reid Institute (ARI) poll added to the chorus of bad polling news for the Liberals. It showed the margin between those who think a change of government is needed and those who don't increasing by 10 points since June. It also showed that 36 per cent of Canadians thought the Conservatives were "the best party to form government," three points up on the Liberals.

But that's not the same as asking Canadians how they would vote if an election were held today. That difference has consequences. One obvious example is in Quebec because the Bloc Québécois cannot form government. Indeed, ARI recorded lower support for the Bloc with this question than other pollsters have when asking about voting intentions.

Using this question, ARI found the Liberals holding an average lead of just two points over the Conservatives in the first two quarters of 2017. Other pollsters gave the Liberals an average lead of eight points in voting intentions over that time — suggesting it's not an apples-to-apples comparison, even if the worsening portrait bodes ill for the government.

Few signals of long-term movement

While these polls were grabbing attention, a few other surveys were released showing little movement in support.

An Ipsos/Global News poll showed absolutely no change since a previous survey conducted in March, giving the Liberals an edge of seven points. The four-week rolling Nanos Research poll, showing the same Liberal lead, has hardly budged since before the summer, though it has shown a Liberal decrease from a recent high in August.

And an early September poll by Campaign Research showed the Liberal lead widening by three points to 12 since July.

Recent decrease in Liberal support

But focusing on these positive polls for the Liberals would be as wrong-headed as cherry-picking the ones that show the party in trouble.

The lesson to be drawn from all of these conflicting polls is not that some are false or that all are unreliable due to their inconsistency.

Taking into account the context of the individual polls, there is a broad trend against the Liberals. This trend appears to indicate a summer bump that has receded. Whether the Liberals will continue to drop remains to be seen.