Canadian Prime Minister Justin Trudeau addresses the media regarding photos and video that have surfaced in which he is wearing dark makeup on September 19, 2019 in Winnipeg, Canada. John Woods | Getty Images News | Getty Images

Canadian Prime Minister Justin Trudeau appears to be on the brink of losing his parliamentary majority. Voters will head to the ballot box to elect their new prime minister on Monday, bringing an end to six weeks of campaigning that has been light on policy and heavy on personality. The latest opinion polls show Trudeau's Liberals and Andrew Scheer's Conservatives running practically neck-and-neck, though — crucially — neither is positioned to win an outright majority. It has raised the possibility of one of Canada's smaller parties playing kingmaker immediately after election day.

Personality vs. policy

Despite overseeing a relatively strong jobs market and with unemployment levels near record lows, Trudeau's fight to stay in power has seen many in the country question his authenticity. That's because in mid-September it emerged that the Liberal party leader had worn blackface make-up on at least three occasions decades ago. The scandal showed Trudeau to be "privileged in the worst sense," Barry Kay, a political science professor at Wilfrid Laurier University in Waterloo, Ontario told CNBC via telephone. "The most revealing thing to me was not so much that it happened, it is that he could not remember how many times it had happened." It was "a case of stupidity, bad judgment and a lack of character," Kay said.

Conservative leader Andrew Scheer and Liberal leader Justin Trudeau gesture at the Federal Leaders Debate in Gatineau, Quebec on October 7, 2019. Sean Kilpatrick | AFP | Getty Images

The photos of Trudeau in blackface make-up were at odds with his oft-stated position as a leader seeking to improve the life of minorities in Canada. It also appeared to tarnish his carefully curated global image as a progressive leader. Trudeau has repeatedly apologized for the racist images, describing his past behavior as "unacceptable." "It will most likely not be a deal-breaker for most Liberal supporters," Jean-Francois Daoust, an expert in public opinion at Montreal's McGill University, told CNBC via email. "However, it damages the image of their leader, for sure."

Obama endorsement

Standing alongside Trudeau at a televised debate last week, Conservative party leader Andrew Scheer described the sitting prime minister as a "phony and a fraud" who does not deserve to govern. Trudeau told reporters in Montreal on Wednesday that he believed the Conservatives had run "one of the dirtiest, nastiest campaigns based on disinformation that we have ever seen in this country." Later that same day, the 47-year old received an apparently unprecedented endorsement from former U.S. President Barack Obama. Tweet 1 In a tweet, Obama said he had been "proud" to work with Trudeau when he was in office, before adding "the world needs his progressive leadership now." Trudeau responded: "Thanks my friend."

'The environment, the environment and the environment'

In the weeks following the blackface make-up scandal, Trudeau has sought to shift the focus onto other issues, framing the election as a de facto referendum on the country's approach to the climate crisis. Agathe Demarais, global forecasting director at the Economist Intelligence Unit (EIU), summarized the most important issues in the Canadian election: "The environment, the environment and the environment." "There is a lot of friction about this issue and it is something that has really polarized people in the country," Demarais told CNBC via telephone.

Led by Swedish climate activist Greta Thunberg (C), young activists and their supporters rally for action on climate change on September 27, 2019 in Montreal, Canada. Hundreds of thousands of people are expected to take part in what could be the city's largest climate march. Minas Panagiotakis | Getty Images News | Getty Images

Speaking in the only official English language debate before the election, Trudeau said Canadian citizens had a choice "between two parties that have very different views on climate change." The Liberals have claimed that, if re-elected, they will try to reach net-zero carbon emissions by 2050 and will exceed 2030 carbon emission goals. Meanwhile, the Conservatives have proposed to eliminate the carbon tax — a contentious policy introduced by Trudeau's government — and focus on incentives rather than punishments for exceeding carbon limits.

Who are the kingmakers?

With the Liberals and Conservatives struggling to attract enough support to govern alone, some of Canada's smaller parties could be relied upon to form a parliamentary majority. A Nanos Research poll published Wednesday put Scheer's Conservatives on 31.5%, with Trudeau's Liberals narrowly behind on 31%. The left-leaning New Democrats, led by Jagmeet Singh, appear to be the most obvious choice of partner for a Liberal minority government, polling at 19%. Singh has indicated he would be open to forming a government with Trudeau, although the incumbent has insisted that he needs a fight for a parliamentary majority in order to stand up to President Donald Trump.

NDP Leader Jagmeet Singh gestures as he speaks during a rally in Montreal, Quebec, Canada, on October 16, 2019, ahead of upcoming legislative elections. SEBASTIEN ST-JEAN | AFP | Getty Images