You may not know it yet, but what NDP leadership candidate Brian Topp thinks matters. It’s true.

A Leger poll released Monday explains why. Topp’s main rival, NDP MP Thomas Mulcair, is heartily disliked by pretty much everyone — including members of his own party. Outside of Quebec, Leger found, only 3% of self-identified Dippers favoured the ambitious Mulcair. In the race to replace Jack Layton, party president Topp seems to be the acknowledged favourite.

That’s not all. To the chagrin of federal Conservatives and Liberals, the NDP brand remains impressively popular, Leger found. Nationally, the Cons are pegged at 39% — but the NDP remain highly competitive, at 33%. That strongly suggests the so-called Orange Crush was no mere blip. Nationally, the NDP remain a factor, and need to be taken seriously.

In Quebec — the province that propelled the New Democrats to a historically high showing in the House of Commons — the federal party still enjoys an astonishing 43% support. The Tories and the Grits are far behind, at 19% and 11% respectively. Topp was born and raised in Quebec, and knows well the crucial importance the province plays in both the House of Commons and in New Democrat backrooms.

Another finding in the Leger poll presents the well-liked Topp with a dilemma, however.

The pollster found that most Liberals support the idea of a federal NDP-Liberal merger. But most New Democrats — some 58% versus 32% — oppose uniting progressives in a single political party.

For Topp, that finding is a dilemma because he’s seen as the leadership candidate who most closely associated with NDP-Liberal detente.

In 2009, Topp was the driving force behind the push for Liberal-NDP coalition government. His plan failed only because then-Liberal leader Michael Ignatieff mistakenly thought he could beat Stephen Harper without the support of New Democrats.

Topp later wrote a compelling book about the machinations going on behind the scenes, in which he sounded wistful about the outcome. Indeed, the book was titled How We Almost Gave the Tories the Boot. Knowing that card-carrying Dippers are currently unenthusiastic about a marriage with the federal Grits, Topp can now be seen choosing his words very carefully. Last week, in fact, this space received some intriguing musings from Topp’s camp.

“We don’t have to become Liberals to win,” said the source. “A merger with the Liberal Party of Canada is not on anyone’s agenda.” But. There’s a fascinating, crucial “but” coming out of Team Topp (and, in fairness, other New Democrats). Said the source: “The thing people liked most about Jack Layton was his willingness to work with others in Parliament — witness the ’08 coalition.” Long pause. “We must not throw this away,” said the senior New Democrat.

I don’t know about you, but that doesn’t sound very much like a categorical “no” to a NDP-Liberal get-together. The source agreed, adding, “There are other tools in the tool box.” There could be an accord, said the source, there could be case-by-case co-operation, there could be an accord like the one hammered out by Mike Pearson and Tommy Douglas.

What’s it all mean? Maybe nothing. But one thing’s for sure: There’s only one NDP leadership contender who should matter to Stephen Harper.

And his name is Brian Topp.