Mr Trudeau rose to international fame when he became Canadacs second-youngest prime minister in 2015 but a combination of scandals have damaged his political standing.
Polls indicate the Liberal Party leader could lose to the opposition Conservative Party on Monday or win but lose his majority in parliament and have to rely on an opposition party to stay in power.
Not in 84 years has a first-term Canadian prime minister with a parliamentary majority lost a bid for re-election.
An Ipsos poll on Sunday showed the Conservatives with a slight 2-per-cent lead over the Liberals, while a poll average by the Canadian Broadcasting Corporation showed the Liberals narrowly leading by 0.4 per cent.
Mr Trudeau is the son of Liberal Party icon and former prime minister Pierre Trudeau. His 2015 victory reasserted liberalism in Canada after almost 10 years of Conservative government and his presidency has been viewed as a beacon for liberals in the era of Donald Trump.
However, political scandals involving attempted interference in the justice system and the resurfacing of old photos of Mr Trudeau in blackface and brownface have cast doubt on his judgement.
In the interference scandal, Mr Trudeau’s former attorney general said he pressured her to halt the prosecution of a Quebec company, causing the Conservatives to call for the prime minister’s resignation.
On Wednesday, Barack Obama made an intervention unprecedented by a former US president when he urged Canadians to re-elect Mr Trudeau.
“The world needs his progressive leadership now, and I hope our neighbours to the north support him for another term,” Mr Obama wrote.
No party is expected to get the 170-seat majority needed in parliament so some kind of alliance may be needed to pass legislation.
If Conservatives win the most seats – but not a majority – they are expected to try to form a government with the backing of Quebec’s separatist Bloc Quebecois party. Mr Trudeau’s Liberals would likely rely on the New Democrats to stay in power.
His rival, opposition leader Andrew Scheer, is a career politician who has been described by those in his own party as bland. Mr Scheer has called Mr Trudeau a “phony” and a “fraud” who does “not deserve to govern this country”.
Jason Kenney, Alberta’s premier and a close friend of Mr Scheer, calls the Conservative leader “an extremely normal Canadian” who is so nice he “can’t fake being mean”.
At a rally on Saturday, Conservative Party supporters chanted “Lock him up!” after the opposition leader said he would investigate Mr Trudeau’s interference scandal, mirroring the “Lock her up!” chants used against Hillary Clinton at Trump rallies.
Mr Scheer, who appeared uncomfortable with the chant, tried to get the crowd to stop and told them to use the phrase “Vote him out” instead.
Mr Trudeau’s liberal government has legalised cannabis nationwide and embraced immigration, at a time when the US and other countries have introduced stricter border controls.
He has also attempted to balance environmental reforms with protecting the economy, leading to criticism from both the right and left of Canadian politics.
Mr Scheer has campaigned on promises to end Mr Trudeau’s carbon tax and cut government spending, including foreign aid, by 25 per cent.
“That money belongs to you, not to them,” Mr Scheer said.
Additional reporting by agencies