Four years after he made it, Justin Trudeau's promise of electoral reform haunts him still.

But while reform is a nagging headache for Trudeau, it is still the dream of proportional representation's advocates, including Jagmeet Singh's New Democrats — even if it's rather unclear how any leader could now promise to move forward with the sort of change that Trudeau rejected.

While the greater question of whether Trudeau has lived up to his promises is at least debatable, when it comes to electoral reform, the answer is fairly straightforward.

In June 2015, Trudeau vowed that the federal election of that year would be the last conducted under the first-past-the-post system. In February 2017, as prime minister, he decided to walk away from that commitment.

Whatever the merits of that decision (Trudeau had misgivings about the ramifications of moving toward proportional representation and feared that a national referendum would be divisive), electoral reform is easily classified as a "broken" promise — an example readily available whenever a critic or political rival wants to assess the Trudeau government's four years in office.

Regardless of how many (or few) Canadians were eager to see the electoral system changed, that abandoned commitment has become a totem for the argument that Trudeau has failed to live up to expectations.

What do Canadians want?

But then, there's also what happened after Trudeau broke that promise — when actual voters were asked whether they wanted to adopt reform through referendums in British Columbia and Prince Edward Island.

In December 2018, British Columbians voted against moving to proportional representation by a margin of 61 per cent to 39 per cent. Four months later, in Prince Edward Island, the vote was different but the verdict was the same, with Islanders saying no to proportional representation by 52 per cent to 48 per cent.

Ballots from B.C.'s electoral reform referendum are counted in Victoria, B.C. on Dec. 11, 2018. (Michael McArthur/CBC)

Those results don't change the fact that Trudeau promised electoral reform, nor do they answer questions that might be asked about how his government approached the issue after it came to office.

But those two referendums suggest a significant number of Canadians share the prime minister's discomfort with proportional representation. The two votes also underline the risk that a national referendum would have produced a narrow or divided result that broke down along provincial or regional lines.

Still, those results have not deterred the New Democrats from promising to move forward with a change to a mixed-member proportional representation system should they form government after this fall's federal election.

Reform first, referendum later

As laid out by the NDP in June, a citizens' assembly would be struck to work out the details of a mixed-member system (MMP). But that system would not initially be put to the general public via a referendum. Instead, it would be passed into law in time for the next federal election. Then, after the new system had been in place for two elections, a referendum would be held to determine whether Canadians wished to stick with it or return to the old model.

A confirming referendum is not unheard of: New Zealand conducted one in 2011, fifteen years after it moved to MMP. But, in that case, the move to MMP was preceded by two referendums — one to ask whether New Zealanders wanted to move away from first-past-the-post, a second to ask whether they wished to adopt MMP.

Not bothering with a referendum beforehand would certainly make it easier to implement reform — but on what basis could an NDP government claim a mandate to do so? It could point to the clear commitment in its platform and the fact that Canadians had elected a sufficient number of NDP MPs to form a government.

But that could tangle the NDP in its own logic.

It is the NDP's position that the current first-past-the-post system is unfair and inequitable, particularly insofar as it allows a party to win more than 50 per cent of the seats in Parliament without necessarily winning 50 per cent of all votes cast across the country. But barring the election of an NDP government with more than 50 per cent of the popular vote (or perhaps an NDP-Green government with more than 50 per cent between them), New Democrats would be left trying to explain how first-past-the-post could produce a mandate to overhaul the electoral system.

Even then, there would still be the small matter of those referendums in British Columbia and Prince Edward Island to account for.

All of this is rather theoretical, particularly with NDP polling at 15 per cent. But coming third in the election would not necessarily prevent the New Democrats from trying to push for reform.

When he was running to be leader of the NDP in 2017 — after Trudeau had walked away from electoral reform, but before the results in B.C. and P.E.I. — Jagmeet Singh was asked whether he would make electoral reform a condition for supporting any minority government after 2019.

"In a minority Parliament, I would consult with our caucus and advocate for the inclusion of proportional representation as a condition of any alliance or support for a minority government," Singh told Fair Vote Canada, an activist group that has been pushing for PR for nearly 20 years.

Based on current polling, it's not inconceivable that October's election could leave a smaller Liberal government needing the support of New Democrats to remain in office. In that case, Singh could try to insist on electoral reform in exchange for the votes of NDP MPs.

At the very least, that would give Trudeau a chance to reject electoral reform for a second time.