The harsh spotlight of their first turn as official Opposition without an established leader may be taking an early toll on the NDP.
The latest survey by The Canadian Press-Harris Decima suggests the New Democrats under rookie interim leader Nycole Turmel are slipping in key regions and most demographic groupings.
Nationally, polls suggests NDP support has been trending downward for about a month.
The latest poll suggests it has fallen to 29 per cent, down from the mid-30s in August and about two points below its May 2 vote share.
Overall, the poll suggests the Conservatives solidly remain Canada's most popular party with 36 per cent support; the Liberals are in third place at 22, while the Greens and Bloc Quebecois are in single digits.
The telephone poll of 2,000 Canadians was conducted Oct. 27-Nov. 6 and is considered accurate within plus or minus 2.2 percentage points, 19 times in 20.
The results don't point to an NDP collapse, but they give credence to MP Pat Martin's recent lament that the party's six-month leadership race may be exerting a price on its performance in Parliament.
The national standing may also be somewhat flattered by a leading 36 per cent count in British Columbia, where the federal brand may be getting a boost from its popular provincial wing.
The most troubling aspect of the new poll for the NDP, said Doug Anderson, senior vice-president of Harris Decima, is that the party is indicating marked erosion of support in Quebec, where it made an historic election breakthrough, and to a lesser extent also in Ontario.
Although its poll results still lead in Quebec at 36 per cent, that is seven points below its election result.
"No party should be fretting right now because they have a long way to go before the next election," Mr. Anderson said.
"But I would be particularly worried about what is going on in those two most-populous provinces, one of which (Quebec) delivered an incredible amount of seats nobody would have predicted."
Of the NDP's 103 seats won, 59 came from Quebec.
"Is that something you can count on again, or is it something you lose as fast as you gain it?" asked Anderson.
After supplanting the Liberals in both seats won and popular vote in Ontario during the election, the poll suggests the New Democrats have fallen well back into third place at 21 per cent, compared to 33 per cent for the Liberals and 38 for the Conservatives.
The party also appears to be losing ground from the summer and from the election standings across most demographic groupings.
In the past month, its level of popularity appears to be trending downward among men and women, and in both urban and rural areas.
The polling cannot determine precise reasons for the apparent cooling of affections, Mr. Anderson said, but there is no doubt the loss of popular leader Jack Layton to cancer in mid-August was a big blow.
Having several party heavyweights pursuing personal agendas in seeking to replace Mr. Layton likely also hasn't helped.
In a recent interview with The Hill Times, leadership candidate Mr. Martin complained that the race is too long and is depriving the party of the best and brightest in the Commons.
"It's agonizing and it's getting very difficult to hold our own as the official Opposition without a leader. We're managing, but we're treading water," he is quoted as saying.