The 2015 federal election will require political parties to work harder than ever to capture the attention of the electorate. This story is part of Adam Radwanski's new assignment looking at how the party machines across the country are preparing.

Jockeying for position in advance of this year's election, Liberals and New Democrats are locked in an ongoing spin battle about whether Justin Trudeau's party could win enough seats to form government.

It's not just that they enjoy amateur punditry. As they fight over those voters that intensely dislike the Prime Minister, the opposition parties know perceptions about who is capable of beating him could make or break their campaigns.

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Even many Liberals concede that – especially in Quebec, where New Democrats hold most seats but anti-Stephen Harper sentiment is believed to run especially high – their chances revolve largely around convincing the electorate that a vote for the NDP is wasted. Conversely, New Democrats know that allowing the Liberals to make that case would make it difficult for them to keep many of the seats they claimed in the past election, let alone have a shot at government themselves.

The issue of whether centre-left voters should strategically vote Liberal to beat Conservatives is not new. But it has taken a new form, because of an existing political map the likes of which the country has never before seen.

In the past, there was never really any question that the Liberals were more competitive than the New Democrats. So the NDP highlighted ideological differences, leaning heavily on variations of "Liberal, Tory, same old story."

The 2011 election seemed to turn that equation on its head. For a time after it won Official Opposition, it appeared the NDP would be the only opposition party able to credibly claim it could form government.

Now, matters have been complicated by opinion polls consistently showing the Liberals neck-and-neck with the Conservatives and the NDP back in third. To the NDP's great annoyance, much of the media are again casting the Liberals as the primary threat to the Tories. So as they try to prevent that narrative from further taking hold, New Democrats have taken to highlighting the sheer difficulty for the Liberals in going from the 35 seats they hold now to a plurality (let alone majority) of the 338 seats in the next parliament.

Liberals counter by enumerating enough ridings to show how they could come out ahead, expressing optimism about virtually sweeping Atlantic Canada, picking up the bulk of seats in Ontario, taking away many of the NDP's Quebec seats and making inroads in the urban west. To make their respective cases, the parties seize on whatever scant evidence is available – which is why, for instance, they're both still fond of mentioning a by-election more than two months ago that neither of them won.

Finishing a relatively strong second in the Whitby-Oshawa riding left empty by the death of Jim Flaherty is still held up by Liberals as a sign of competitiveness, because by their account it's one of the toughest Toronto-area seats for them. They point to the dismal 8 per cent earned by the NDP, after that party's second-place showing last campaign, as evidence of where momentum is.

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Nonsense, reply the New Democrats. More so than their own party, they say, the Liberals need to win ridings such as Whitby-Oshawa to have a chance at government. The fact that they hyped their chances and then fell short is evidence that the Liberals' talk of momentum is overblown.

An obvious problem for the NDP, as it points out the Liberals' challenges, is that party's own struggle to explain its path to power. When pressed, New Democrats can point to a handful of potential pickups in Quebec, a bunch in Northern and Southwestern Ontario, a few in Saskatchewan, and up to 10 in British Columbia. But to eke out a plurality, they'd likely have to win almost all those and scarcely lose any of their existing seats.

For the Liberals, meanwhile, raising expectations is a double-edged sword; if they're too effective at it, anything short of winning government could cause an internal bloodletting. And as members of Mr. Trudeau's team readily acknowledge, their party has a history of suffering for its perceived arrogance.

For now, the Liberals are trying to show their competitiveness by flexing their organizational muscle – touting big membership tallies, fundraising totals and hotly contested nominations in key ridings – and continuing that spin war with the NDP mostly behind the scenes. More public debates, for the next while, will be about policy, personality and suitability for office. But as the election draws closer, the battle around winnability will become more overt.