Prime Minister Justin Trudeau is seen in the House of Commons in a file photo. iPolitics/Matthew Usherwood

The Trudeau Liberals have regained the lead in the federal horse race with just over 100 days before October’s election, suggests a new Mainstreet Research poll for iPolitics.

However, the governing party’s narrow 1.8 percentage point lead over the Tories falls just within the margin of error for the phone survey of 2,651 adults (18 and older), conducted between June 27 and July 2.

In the new survey released Tuesday, the Liberals have the support of 35 per cent of decided and leaning voters, compared to 33.2 for the Conservatives. The NDP sits only a tenth of a percentage point ahead of the Greens in third place with 10.4 per cent of support.

Meanwhile, the Bloc Québécois pulled 4.5 per cent of support nationally (it was only tested in La Belle Province), while Maxime Bernier’s right-wing populist People’s Party of Canada (PPC) was the top choice for 4.6 per cent of respondents. The margin of error for the poll is plus or minus 1.9 percentage points, according to Mainstreet.

When including undecided voters, the Liberals are up on the Tories by a smaller 30.2-29 per cent margin, with the NDP and Greens tied for third at 8.5 per cent. The PPC sits at 4.2 per cent and the Bloc is at 3.8, with the undecideds making up 14.1 per cent.

Compared to Mainstreet’s last poll in April, the Liberals (among decided and leaning voters) are holding steady, the NDP is down slightly, the Greens are up roughly 2.5 points and the Bloc and PPC are enjoying a small uptick. But it’s the Conservatives who have seen the most significant movement, shedding 4.2 percentage points since the spring survey.

“The Liberals have rebounded thanks to a dip in Conservative support,” Quito Maggi, president and CEO of Mainstreet Research, said in a statement.

Thanks to “significant” leads in Ontario, Quebec, and Atlantic Canada, Maggi said the Liberals would be the “favourites to win if the election were held today based on these numbers.”

In Canada’s most populous and thus vote-rich province, the Liberals lead with 41.6 per cent of support among leaning and decided voters, compared to 32 per cent for the Tories, 11.5 per cent for the NDP, 9.1 per cent for the Greens and 4.3 per cent for the PPC.

The margins of errors for the regional breakdowns are larger than the national results because of the smaller sample size. For Ontario, the margin of error is plus or minus 3.5 percentage points, according to Mainstreet.

In neighbouring Quebec, the Liberals top all parties with 36.7 per cent of support, while the Tories have supplanted the NDP and Bloc in the runner-up spot at 22 per cent. The aforementioned Bloc and NDP are polling at 19.1 and 8.6 per cent, respectively. The Greens are a close fifth with 8.2 per cent of support.

For the NDP, the numbers, if they panned out on election day, would represent a colossal drop in support over the past eight years. In the party’s historic best showing in the 2011 election, it took 42.9 per cent of all ballots cast in Quebec and 59 seats in the province. In the 2015 vote, that was reduced to 25.4 per cent and 16 seats.

The numbers for Quebec have a margin of error of plus or minus 3.3 percentage points, says Mainstreet.

Perhaps unsurprisingly, the Tories hold a large lead over the Liberals in Alberta (57.4-21.4 per cent) and the Prairies (47.8-30.1), which for the poll’s purposes refer to Manitoba and Saskatchewan. The Conservatives are also ahead in election battleground B.C., with the Andrew Scheer-led party up on the Liberals by five points (30.7-25.7 per cent). This falls outside the 4.8 percentage point margin of error for the province’s results.

The Greens, whose two current seats are both located in B.C., are a very strong third in the Pacific province with 21.5 per cent of support, while the NDP is a distant fourth at 13.7 per cent.

The People’s Party is strongest in Alberta (6.9 per cent) and weakest in Quebec (3.8), according to the poll results. Bernier, who represents a Quebec riding, often bills himself as “the Albertan from Quebec” because of his libertarian-esque views.

In Atlantic Canada, the Liberals are leading the Tories 37.5 to 29.4 per cent, while the Greens, buoyed by recent successes in the region on a provincial level, are third at 17.5 per cent.

Mainstreet says results for the region come with a margin of error of 7.6 percentage points.

The New Brunswick Green Party won three seats in that province’s most recent election last fall, while the P.E.I. chapter formed the Official Opposition after that province’s election in May by grabbing eight seats.

The next federal election is tentatively scheduled for Oct. 21.