Justin Trudeau's Liberal party spent just over $43 million to win last fall's federal election — $1.2 million more than Stephen Harper's Conservatives.

That the third party outspent the governing party — which changed election rules and called an extended campaign in an apparent bid to give the deep-pocketed Conservatives a financial edge over its competitors — surprised even Liberals.

But Liberals say they believe it's how the two main parties spent their money, not how much, that made the difference between winning and losing.

The Liberals spent more than four times as much as the Tories on digital advertising and digital voter contact.

But they spent less than one-fifth of what the Conservatives spent on voter contact calling services — a tool the Tories used to great effect in previous campaigns but which Liberal strategists say is now an "archaic" and ineffective way of reaching voters.

'Quicker, cheaper, easier, better'

The eye-popping spending by the various parties during the marathon 78-day campaign is disclosed in campaign financial reports filed with Elections Canada.

"When we heard we had a 78-day campaign ... and we knew the budgets the Conservatives were working with, we had to ask ourselves, 'How are we going to innovate; how are we going to do this so that we can do things quicker, cheaper, easier, better?"' said Tom Pitfield, the Liberals' chief digital strategist for the campaign.

If you're not on digital, you're pretty much marginalizing a quarter to a third of your vote - Tom Pitfield , Liberal campaign strategist

"And digital had the greatest ROI (return on investment) ... We focused on it as a strategic advantage."

The financial reports show the Liberals and Conservatives spent similar amounts on traditional television and radio ads: $18.9 million and $17.3 million respectively. Those ads were the single biggest expenditure for both campaigns.

But the Liberals also spent $8.8 million on "other" advertising, what Pitfield said was mostly digital advertising and digital voter contact. The Conservatives spent just less than $2 million on other advertising.

The Tories, meanwhile, shelled out $5.1 million on call centres whereas the Liberals spent just $436,000.

"To contact someone offline ... is an extremely inefficient way of trying to reach people," said Pitfield.

"I think it's largely ineffective. Different campaigners think different things, but my view is it's archaic."

Targeting younger voters

Pitfield reckons the Liberals reached 18 million Canadians — more than half the population — through their online campaign, using Facebook, Google and YouTube not just to advertise but to engage voters in a two-way conversation, figure out their motivations and identify the issues that engaged them the most.

By contrast, he said, "I think the Conservatives focused on ... the old way of doing campaigns," conducting focus groups to find messages that would resonate and then "carpet-bombing" the airwaves and telephone lines.

The problem with that traditional approach is that 25 per cent of Canadians now have only cellphones and 42 per cent of them don't watch television, he added.

"So, if you're not on digital, you're pretty much marginalizing a quarter to a third of your vote."

The digital campaign was particularly helpful in reaching young voters, who turned out in record numbers last fall and are thought to have ensured Trudeau's majority victory. But the youth were also instrumental in helping the Liberals reach a wider audience.

"If you want to reach people, the best way to do it is to reach out to young people because they really do share content," Pitfield said.

"They'll go and tell their mother or their brother or their sister, you know, 'Check this out, you've really got to see this."'