Conservative Leader Stephen Harper, NDP Leader Tom Mulcair and Liberal Leader Justin Trudeau spent much of Thursday's lively leaders' debate clamouring to present themselves as the best choice to manage the economy after Oct. 19.

And while the debate itself may not have changed many voters' minds, five key storylines emerged from the raucous proceedings that may come to define the rest of the election campaign.

1. Trudeau: Now is the time to invest

Liberal Leader Justin Trudeau ​spent much of the debate aggressively selling his plan, telling Canadians now — with interest rates at record lows — is as good a time as any to spend on needed infrastructure and stimulate the sluggish Canadian economy.

Trudeau is the only leader in this campaign promising to run deficits in the short term — up to $10 billion a year over the first three years — and said that makes him the only leader being "honest" with Canadians. 

"It's time to kickstart the economy," he said, staring down the lens of the television camera. "I'm worried about saddling my kids with is a lack of jobs, a lack of good infrastructure, a lack of a future because the government didn't want to invest in our country.

"Mr. Mulcair is putting it off, he's made balancing Stephen Harper's budget his priority which means he can't give Canadians the help they need," Trudeau said.

Trudeau: Now is the time to invest in the economy1:04

Trudeau pointed to top economists to back up his plan, including Kevin Lynch, once Harper's hand-picked choice to lead the civil service.

But Harper said it's a reckless proposition to run deficits just as the country has returned to surplus.

2. Harper: Now is not the time to raise taxes

While the Canadian economy isn't teetering on the brink, the numbers aren't all that rosy, with the low price of oil threatening to cut into government revenues.

As a result, Harper spent part of the night on the defensive.

"Mr. Harper, you have run deficits in good years, in bad years, and the only time you've said that deficits are not going to run is in election years," Trudeau said. 

Mulcair also piled on the criticism.

"Mr. Harper put all of his eggs into one basket, then he dropped the basket," Mulcair said. "Four hundred thousand well-paid manufacturing jobs lost on his watch. There are now 300,000 more Canadians without a job than when the recession hit in 2008."  

But Harper was ready for the attacks. He pointed to a widely-cited New York Times article that heralded the Canadian middle class as the world's wealthiest.

Trudeau, Harper and Mulcair debate pension 'taxes'1:26

"We're making sure we have more money in people's pockets, and we're the only party not talking about raising any of your taxes going forward, or running deficits going forward, and in an unstable global world, this is the kind of plan we need."

"I never said things are great," Harper said twice during the debate, "But in the last 10 years, where would you rather have been in all this global economic instability? Where would you rather have been than in Canada?"

3. Mulcair: Now is the time for responsible change

NDP Leader Tom Mulcair spent much of the debate presenting his party as the moderate choice for change, in contrast to Trudeau's plan for deficit spending.

The NDP is promising to balance the budget for the next four years all the while ramping up social spending on day care and affordable housing, by raising corporate tax rates.

The adherence to fiscal prudence has angered some of the more leftist elements of the NDP who are upset with the party's devotion to balancing the books.

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But Mulcair's seemed intent on assuaging fears an NDP government would hike taxes and leave the budget in tatters.

"Mr. Trudeau's plan is frankly reckless and it's uncosted," Mulcair said. "He is proposing to dump tens of billions of dollars in new debt on the backs of future generations."

That prompted Harper to invoke the ghost of Bob Rae's Ontario NDP government of the early 1990s.

"Mr. Mulcair's plan is the same NDP playbook," Harper said. "We saw it in British Columbia, we saw it in Ontario, we're seeing it in Alberta, a whole bunch of spending."

4. Refugees, security and 'fear-mongering'

A question on the role of immigrants in the economy opened the debate up to another issue that has dominated the campaign: refugees fleeing war into Europe. Harper has faced fierce criticism for his response to the crisis — but he put the choice in stark terms during the debate.

Leaders argue refugee policy at economic debate2:23

"I said we will bring in more," Harper said. "What these guys would have done in the last two weeks is have us throwing open our borders and literally having hundreds of thousands of people coming [in] without any kind of security check or documentation.

"That would have been an enormous mistake."

The other leaders accused Harper of fear mongering. Mulcair invoked retired Gen. Rick Hillier, Canada's former top general, who said Canada should "stop being frightened of our own shadow." 

No one, said Mulcair, is suggesting dropping all screening for refugees.

"Mr. Harper, why don't you stop using the security excuse as a pretext to do nothing," Mulcair asked.

Trudeau also jumped on a reference Harper made to "new and old-stock Canadians."

"The fact that he referred to something called 'old stock Canadians' demonstrates that yet again he is choosing to divide Canadians against another," Trudeau said in the post-debate scrum.

5. Contrasting styles

Trudeau was undoubtedly the most animated leader on the Globe and Mail stage, speaking quickly and more loudly than his rivals. He was aggressive, interrupting the other leaders and moderator David Walmsley on a number of occasions.

"That's not true Mr. Harper," Trudeau said four times in the span of a minute, when Harper accused him of being lax on security screening for refugees.

He also stuck to his message, repeatedly circling back to his plan to invest in infrastructure.

Mulcair, for his part, presented a deliberately calm demeanour, speaking in measured tones to slow the pace after particularly feisty exchanges. At times, his approach meant he was left out of the discussion.

Harper did not shy away from attacks, but as in the first debate seemed content to watch Trudeau and Mulcair engage each other until he had the chance to defend his record again and repeat his familiar campaign themes.