Trudeau, 49, is eyeing September for what would be his third election, sources said.

He first won a majority in 2015. But in a federal vote two years ago, after decades-old blackface pictures surfaced, Trudeau came up short of a majority, forcing him to depend on opposition parties to pass legislation.

The Liberals need to pick up just over a dozen more seats in the 338-seat House of Commons to be able to govern on their own.

A September vote would be "an election of inches, not giant steps. We're looking at 15 seats or so," said Allan Tupper, professor of political science at University of British Columbia at Vancouver.

"Failure would be not to win a majority ... and repeat the status quo," Tupper said.

If Trudeau were to get only another minority, it would almost certainly lead to questions about whether the party needs a fresh face, analysts said.

The official opposition Conservative Party has consistently lagged in polls, suggesting Canadians could reward the Liberals for their handling of the pandemic.

There are precedents that look promising for the Liberals. Four of Canada's 10 provinces held elections during the pandemic with the sitting government winning every time.

Pollsters say there is a window this autumn in which the Liberals could win a majority, as Canadians embrace the freedom of being vaccinated and the latest budget injects billions of dollars into the economy.

Nationally, Liberals would win 34 per cent, compared to 29 per cent for the Conservatives and 22 per cent for the left-leaning New Democrats, pollster Leger said in a survey published last Wednesday.

That is probably still short of a majority, but polls by other companies have put the Liberals further ahead.

The timing of the election is important "because the pandemic has been a highlight in the Liberal government's performance in the eyes of Canadians," said Shachi Kurl, executive director of polling firm Angus Reid Institute.

In the first quarter, 45 per cent of adults said the COVID-19 response was by far the top issue on Canadian voters' minds, but in the third quarter it was the ninth issue at 19 per cent, an Angus Reid poll from July 16 shows.

"So Justin Trudeau now has to stay in this sweet spot wherein the pandemic is still on the minds of Canadians," Kurl added.

COVID-19 case numbers are down dramatically, as are hospitalisations and deaths, and vaccination levels are among the highest in the world.

The Bank of Canada earlier this month painted an optimistic picture of growth heading in the second half of the year.

But another potential source of trouble is that - instead of fading from peoples' minds - COVID-19 will come roaring back as more contagious virus variants spread, as is happening in the US, Australia and elsewhere.

"The reality is that with the Delta variant and other variants of concern out there, it is likely that we will see a rise in cases over the coming months," Trudeau said on Tuesday.

If the Liberal leader were to fall short of a majority for a second time, it might be an indication that voters are growing tired of Trudeau, triggering talks of succession.

"There are still a number of Canadians who like Justin Trudeau very much, but in terms of that mania, that fever, that passion for Justin Trudeau - that is long gone," Kurl said.

Australian Associated Press