If you're still enjoying your Labour Day weekend, please don't let the prospect of an election call spoil it.

Even though the federal campaign could begin officially at any time now, the last possible date for calling one is September 15. That's the latest date that would satisfy the minimum campaign length of 36 days before voting day, fixed in law as "the third Monday of October in the fourth calendar year following the previous general election" — October 21, 2019.

New election rules mandating that campaigns can only run a maximum of 50 days mean Liberal strategists have less room to manoeuvre in timing the election call, although there's still a two-week window.

"There's always some strategy involved," said Anne McGrath, a longtime NDP strategist.

It's probably safe to assume that calling an election before Labour Day is not what the Liberals want to do — particularly since Gov. Gen. Julie Payette is out of the country.

In the past, prime ministers have used the power to call elections to work the timing to their advantage.

In 2000, Jean Chrétien called a snap election a mere three years after winning his second majority, because polls indicated the Liberals had a phenomenal lead in Ontario. The gamble paid off.

Conservative leader Stephen Harper pauses for a moment as he addresses the crowd on election night in Calgary in October 2015. (Jonathan Hayward/The Canadian Press)

Stephen Harper wasn't so lucky when he rolled the dice four years ago, betting that a long campaign would benefit his Conservatives — armed with a healthy war chest — at the expense of his opponents. When pressed by reporters, he said the opposition parties were already campaigning and he wanted a level playing field.

Harper launched a 78-day campaign, the longest in modern times. The move backfired.

"What it did seem to do," said Richard Ciano, a past president of the Progressive Conservative Party of Ontario, "is give Justin Trudeau, the then-leader of the third party, a chance to really run a good retail campaign."

The conventional wisdom says shorter campaigns are better for incumbent governments.

'Tighter and shorter'

"A long campaign tends to give you a longer time for something to sideswipe you, for an issue to come up that you didn't expect, and that's never a good thing for a campaign and rarely for a government," said Tim Murphy, a lawyer with McMillan LLP who once served as chief of staff to Prime Minister Paul Martin.

"[The Liberals] probably want it to be tighter and shorter, thinking that there's less chance for something to blow up or go off-track," said Ciano.

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Going early would put a stop to Prime Minister Justin Trudeau's ministers fanning out around the country for funding announcements. It also would rob Trudeau of the time he wants to frame a narrative around his opponent, Conservative Leader Andrew Scheer, before hitting the campaign trail.

Any government has to answer a key question before deciding on the timing of an election call, Murphy said.

"Are there issues, irritants, concerns that you would like to have settled or at least calm down before the election starts?" he told CBC, adding that governments use the time before the formal campaign begins to "frame the positive, talk a little bit about what the government has done and is trying to do ..."

Once the writ period officially begins, parties have to submit to a spending limit of just over $28 million.

Federal NDP Leader Jagmeet Singh might benefit from the media's low expectations, says an NDP strategist. (Christopher Katsarov/The Canadian Press)

Longer campaigns cost the parties more. For the NDP, which has struggled with fundraising, that would be a problem.

McGrath acknowledged her party will be constrained this election. "I would prefer it if there was more [money] because it gives you more latitude, but I have seen us do very well with very little."

She said she thinks NDP Leader Jagmeet Singh, whose party is hovering around the 14 per cent mark in the polls, can capitalize on the fact that "the pundits have written him out of the picture a little bit."

"He's not suffering from high expectations," McGrath said, adding that the NDP already has released its full platform so voters know what the party is offering.

For some strategists, what happens at the start of a campaign isn't nearly as important as what happens in its final days.

"Voters wait later and later to actually make their decision," Ciano said. He argues that the last 14 days are the most crucial in a general election campaign — particularly this one, since campaign-style events have been happening all summer.

Those taking bets on when the election will be called should consider two facts. First, it's considered gauche for a prime minister to launch an election campaign while a province is going through one of its own. Manitobans go to the polls to elect a provincial government September 10.

Second, visits to the Governor General to officially dissolve Parliament tend to take place on Sundays — but not always.