With the aura of his star power fading, the Canadian prime minister, Justin Trudeau, and his governing Liberal party are aiming to extend their parliamentary majority for another four years.

As summer winds down, all party leaders are effectively in campaign mode and the prime minister is expected to officially call the election in the coming days. Under current rules, opposition parties will have less than two months to shake the incumbent Liberals from government as they travel the country to woo voters.

The election is predicted to be an acrimonious affair, say pollsters. And as Canadians prepare for the mudslinging, a number of issues are expected to dominate the campaign.

The environment

A spring of intense flooding in eastern parts of the country and wildfires raging in the west has brought new urgency to Canada’s response to the climate crisis.

“For the first time in at least the last 10 years, the environment is actually coming out as the top, unprompted national issue of concern, said Nik Nanos, head of the Canadian polling firm Nanos Research. “[It’s] outstripping both jobs and the economy and healthcare, which are the two traditional issues.”

In addition to a spate of natural disasters, Nanos credits a pitched battle in the country over carbon taxes for keeping the environment as a key electoral issue.

Trudeau is likely to position himself as the leader best equipped to meet the country’s climate obligations, despite the government being far off track for its Paris accord commitments.

While the rival Conservative party has been widely panned for its lack of substantial environmental policies, Trudeau has also received vigorous pushback from climate activists.

In late June, the government declared a climate emergency in the country – and then approved a multibillion-dollar oil pipeline expansion the following day.

“For the Trudeau government to approve this pipeline after declaring a climate emergency makes about as much sense as pouring gasoline on a burning fire,” said Greenpeace campaigner Mike Hudema.

Populism

Amid rising tides of far-right populism in the US and Europe, the election will mark the first country-wide appearance of the People’s Party of Canada – a rightwing splinter party led by the former Conservative minister Maxime Bernier. Ever since its formation, the party has railed against immigration and Canada’s multiculturalism policies.

Like many countries, Canada has witnessed a growing intolerance for immigrants and racial minorities among conservative-identified voters, although analysts are unsure how much support a far-right populist party can expect. Bernier’s low polling numbers have so far disqualified him from the two leader’s debates held in October.

The country’s electoral system typically rewards parties that cater to the centre, said Tamara Small, a political science professor at University of Guelph, where the plurality of votes are up for grabs.

But analysts also see intolerance and xenophobia becoming increasingly concentrated in parties on the right. This recent shift speaks to a hardening of political views across all parties, said Frank Graves, president of the political polling company Ekos Research.

“We’re seeing radical polarization on issues like climate change and … immigration in general,” said Graves. “We’re talking about stuff we’ve never seen before.”

The Green party

The real beneficiaries of any populist wave could be the Green party, said Graves and Nanos.

“The Greens, in my polling, are ahead of the [leftwing New Democratic party], which has never happened,” said Graves – signalling what could prove to be a fundamental reshaping of Canadian politics.

If an election was held in the coming days, he said, “the Greens are very close to the point where they could be the power-broker that kept to a minority government in play.”

Recent electoral success in local and provincial elections has buoyed support for the party and polling also suggests that Elizabeth May, the Green leader – and most seasoned politician currently in federal politics – remains the most popular leader in the country.

Much of the party’s appeal lies in its strong environmental stance, but also its position at the fringes of mainstream politics. Polling shows the Greens drawing support not just from disaffected Liberal voters, who feel the prime minister has not acted decisively on the environment, but also from the NDP – and even the Conservatives, said Graves.

“It looks like the Green[s] … are Canada’s kind of ‘friendly response’ to populism,” said Nanos. “People that are dissatisfied or disenchanted with the system and are disappointed with the mainstream parties are now looking at the Greens as a protest vote against the system.”

On Tuesday, 14 frustrated members of the NDP in the province of New Brunswick announced they would be leaving the party for the provincial and federal Greens.

The wild card

In the summer of 2015, Trudeau was polling a distant third before the autumn election. Seemingly out of nowhere, he surged ahead and secured a robust parliamentary majority.

While surprises could – and probably will – pop up domestically, Nanos predicts a major disruption could come south of the border, from the US president.

“Donald Trump will probably say something that could materially shape the outcome of the election. It could be on purpose. It could be by accident,” said Nanos.

Trump has repeatedly broken with traditional taboos against commenting on foreign elections, weighing in on the UK Conservative leadership race and publicly supporting Benjamin Netanyahu’s re-election campaign as Israeli prime minister.

Any barbs lobbed at Trudeau by the president could rally Canadians around the prime minister, said Nanos, and any endorsement of a Conservative candidate would probably be a “stake in the heart of the Conservative party”, he said.

“Canadians are especially tuned into Donald Trump, whether they love or hate him because, realistically, Canada is hostage to geography.”

The election is likely to be held on 21 October.