New Democrats rejected the leadership of Tom Mulcair at their party convention on the weekend, kicking off a battle for the soul of the NDP. With their support for a closer look at the Leap Manifesto, NDP members seem to believe the party's future lies in a return to the left.

But that edge of the spectrum, if the New Democrats want to occupy it again, will need to be wrested away from the Liberals first.

Polling by the Innovative Research Group conducted at the end of March suggests core constituencies of the New Democrats have abandoned the party in droves, swinging over to the Liberals in massive numbers.

Innovative's polling divides the electorate into a group of voting segments, three of which are of particular importance to the NDP. These are what Innovative calls the "core left," "left liberals" and the "populist left."

The core left is the largest segment for the New Democrats, and believes that government spending should be based on public need and not affordability, that the main role of government is to redistribute wealth and that the environment should be favoured over the economy.

Left liberals also feel that public need and the environment should be paramount, but that the government's role is to create equal opportunity.

The populist left believes in the importance of redistribution and public need, but prefers government policy to be based on common sense rather than expert opinion, is more split on whether to value the environment over the economy, and is more likely than other Canadians on the left to want the government to stay out of the way of business.

Altogether, Innovative estimates that these three segments represent 30 per cent of Canadian voters.

From dominating the left to losing it

In July 2015, when the NDP was leading in the polls nationwide, the party dominated these groups. It had 60 per cent support among the core left, 46 per cent support among the populist left, and 43 per cent among left liberals. The New Democrats were beating the Liberals among all of these segments, with the widest lead being among the core left. The Liberals had just 29 per cent support in this group.

The NDP lost all three of these segments to the Liberals during the campaign.

And the Liberals have deepened their lead among these groups in the months since. They lead the NDP by 24 points among the populist left and by 42 points among left liberals. The Liberals have the support of 64 per cent of the core left, against only 23 per cent for the New Democrats.

A recent poll by Abacus Data also hints at trouble for the New Democrats on the left flank. The Liberals were leading the NDP by a margin of 51 to 26 per cent among centre-left voters in the Abacus survey, and were also ahead among those who self-identified as being on the left by 47 to 23 per cent.

Might the adoption of the Leap Manifesto be the first step towards seducing this portion of the electorate back to the NDP?

Left's core and populists soured on Mulcair

That the party voted to consider the Leap Manifesto over the next two years, despite the pleading of Alberta Premier Rachel Notley for New Democrats not to turn their backs on the resource sector, might have been the first sign that Mulcair had lost the room in Edmonton.

But the Innovative poll also suggested that Mulcair was already losing the party's left flank. At the height of his party's popularity, his net favourability rating among the core left was +75, and +47 among the populist left. By the end of March, days before the leadership vote, that had fallen to +34 among the core left and to just +9 among the populist left.

By comparison, Justin Trudeau's numbers ballooned to +47 from +13 among the populist left and to +77 from +25 among the core left.

Mulcair's numbers held up better among left liberals, dropping from +33 to +24. With his positioning more among this group of the NDP, that might have been the only constituency he still had on his side on the convention floor on Sunday.

When Trudeau and Mulcair were pitted against each other on who voters prefer as prime minister, the NDP leader had also lost a lot of ground. He was beating Trudeau by 43 points among the core left last July. In March, he was being beaten by 55 points, with 70 per cent of this core NDP constituency preferring Trudeau. Left liberals preferred Trudeau by a margin of 74 to 9 per cent.

This is what may pose the biggest problem for the New Democrats going forward, as left-wing Canadians, and not just those more towards the centre-left, have been wooed by Trudeau's Liberal government — though not necessarily for the long term. The good news for the NDP is that a majority of voters within these segments would still consider voting for the party.

But the New Democrats losing the last election and trailing badly in the polls today is not only the result of a failed bid to move to the centre — the shift under Mulcair's leadership might have cost the NDP much of the left as well. That might explain why the party's membership rejected him. The next leader will have to win over the party, but can he or she get Canada's left back too?

The poll by the Innovative Research Group was conducted between March 22 and 30, 2016 and interviewed 2,456 Canadian adults who were members of an online panel. A probabilistic sample of this size would yield a margin of error of +/- 2 per cent, 19 times out of 20.

The poll by Abacus Data was conducted between March 16 and 18, 2016 and interviewed 1,500 Canadian adults who were members of an online panel. A probabilistic sample of this size would yield a margin of error of +/- 2.6 per cent, 19 times out of 20.