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.
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.
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."
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.
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."
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.
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.
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.
Another possible contender for kingmaker status could be the Green Party of Canada. Led by Elizabeth May, the party is polling at 9.5%. May has refused to rule out forming a majority government with either the Liberals or the Conservatives.
A Quebec-based separatist party in Canada's French-speaking province could also make surprise gains at the polls.
"The Bloc Quebecois might be interesting to mention … They could quite easily gain seats (because they had few in 2015 compared to previous performance) and potentially become a 'kingmaker,' that is, obtaining the balance of the power," McGill University's Daoust said.
The Bloc Quebecois, polling at 7%, has said it has no interest in forming a coalition government with anyone.
Looking ahead to Oct. 21, Wilfrid Laurier University's Kay said the main reason none of the major parties appeared to be on the brink of securing a parliamentary majority was quite simple: "None of the leaders are very popular."
— Editor's note: This story has been updated to reflect the latest poll numbers.