United we stand, divided we fall. That was the lesson the Canadian right finally learned in late 2003, when the Canadian Alliance and Progressive Conservative Party merged into the Conservative Party of Canada. While they shared many common policies, the CA and PCs also fought bitterly over such issues as Quebec’s place in Canada. But in the end, the desire for power outweighed any differences — and the result has been nine years of Conservative government.

Unity is a lesson the Canadian left has yet to learn. While so-called “progressives” adhere predominantly to the NDP, a significant number also live within the Liberal party. The fragmented left-of-centre vote has recently denied both the possibility of forming government. Polls show that if a vote were held today, they’d be out of luck again: The Liberals are in the lead for the popular vote, but the Tories are in a position to form a minority due to seat distribution. The NDP brings up the rear in third place.

It is therefore no surprise that in the past few weeks, NDP leader Thomas Mulcair has been musing on the possibility of a coalition government with the Liberals. If the Tories can’t get a majority, then the second- and third-place parties could approach the Governor General and ask to govern together. (This possibility might well have motivated Prime Minister Stephen Harper to continue the current G-G David Johnston’s term past the 2015 election date, in the hopes that Johnston would deny such a request.).

Such talk risks sounding defeatist, of course: Why throw in the towel before the game has officially begun? Au contraire, NDP strategists claim that coalition talk is merely designed to allow left-leaning voters to be more comfortable supporting their party, rather than voting strategically for the Liberals. Mulcair’s colourful claim that Liberal leader Justin Trudeau “slammed the door” on his fingers over the issue also makes it appear that a vote for the NDP would be a vote for a Mulcair-led coalition, not one fronted by Trudeau.

However much the Liberals would like to pooh-pooh it, the coalition question is of huge importance to their party. If the Stop Harper demographic buys into the concept, it could deny the Liberals a return to power. In 2011, Stop Harper voters underpinned the NDP’s Quebec sweep, as Bloc Québécois voters switched their votes in the hopes of unseating the Conservative government. Paradoxically, it also boosted the NDP’s support in Ontario at the expense of the Liberals, and allowed enough Tories to come “up the middle” and win a majority.

This year, the Tories’ appeal to Quebec voters on the basis of security and identity threatens NDP support in that province. In Ontario, the Liberals are running neck-and-neck with the Tories, with the NDP a distant third. B.C. is a wild card, with a three-way race. Unless Trudeau makes a monumental gaffe, or the shenanigans of the Mike Duffy trial expose a treasure trove of Tory secrets, it’s likely to be a contest for first place between the Liberals and the Conservatives — unless progressive voters turn up their noses at Trudeau at the 11th hour.

Which leaves the NDP with every incentive to try to coalesce their way into power. Rather than an admission of weakness, it is a realpolitik recognition that you need a seat at the table to get things done. Unity trumps division, even if that unity is forced, or temporary.

In the long term, however, a coalition is merely a stop-gap, unless it paves the way for something more, such as a merger. While the Canadian right arguably had an easier starting point, and far less history to overcome, the Canadian left has the same incentive to come together: advancing its agenda and creating a winnable progressive alternative. Until they do so, it’ll be a case of the right vs. the middle, over and over again.

Tasha Kheiriddin/The National Post/March, 2015