All three major parties are locked in a virtual tie for support, despite regional shifts that have seen the NDP lose ground in Ontario over the past month.

Despite a week of headlines from the Mike Duffy trial, questions over energy projects, and worrying economic reports, the parties showed little change in their national numbers, according to the latest Nanos Research weekly ballot tracking.

Here are the latest numbers, with the percentage-point change from the previous week in brackets:

Conservatives: 30.1 per cent (-1.7)

Liberals: 29.9 per cent (+1.2)

NDP: 29.1 per cent (+0.1)

NDP Leader Tom Mulcair has spent much of his time campaigning in Quebec, where his party enjoys its highest support. That may explain falling numbers in Ontario, where the NDP are in third place at 21 per cent.

The New Democrats stood at 23 per cent the previous week, and 26 per cent the week before that, down from a high of 30 per cent for the week of July 17.

The Conservatives have had steady support in Ontario, with Stephen Harper making several campaign stops to the vote-rich Greater Toronto Area.

Quebec is a far different story, with the New Democrats riding keeping a strong lead at 37 per cent, despite a slight boost in support for the Bloc Quebecois, which now sits at 19 per cent. The Conservatives trail behind in Quebec with 12 per cent support.

Methodology:

The regional numbers have sample sizes ranging from 80 respondents in Atlantic Canada to 257 in Ontario, which means they have a wider margin of error than the survey overall.

A random telephone survey of 1,000 respondents is considered accurate within plus or minus 3.1 percentage points, 19 times out of 20. The weekly ballot tracking is determined using random landline and cellphone interviews with 1,000 adult Canadians, and may be weighted by age and gender. The current report is based on a four-week rolling average up to and including Aug. 21, 2015.