OTTAWA - A new poll suggests the federal Liberals are rebuilding their strength in Quebec and at year-end may have been in a dead heat with the Conservatives in support across the country.

As rumours swirl about a possible shuffle in Prime Minister Stephen Harper's cabinet and commentators muse about a possible spring election, the new poll data suggest that support for the two main parties is on a see-saw.

The Decima Research survey conducted December 27-30 and provided exclusively to The Canadian Press, suggests the Conservatives had 34 per cent support nationally, compared with 31 per cent for the Liberals. The difference is within the poll's 3.1-percentage-point margin of error.

The survey also indicated the NDP had 15 per cent support, the Bloc Quebecois 10 per cent and the Green party eight per cent.

In an earlier Decima poll last month, the Conservatives were at 32 per cent, compared with 35 per cent for the Liberals, placing the parties in a virtual tie then as well because of the margin of error.

In the last election, the Tories took 36.3 per cent of the vote across the country. The Liberals had 30.2 per cent, the NDP 17.5, the Bloc 10.5 and the Greens 4.5.

The latest survey numbers suggest the Liberals had an edge on the Tories in Ontario and Quebec.

The poll gave the Liberals 40 per cent support in Ontario, compared with 35 per cent for the Conservatives, 13 per cent for the NDP and 11 per cent for the Greens.

In Quebec, the Bloc had 41 per cent, compared with 27 per cent for the Liberals, 14 per cent for the Tories, 11 per cent for the NDP and five per cent for the Greens, although the margin of error for regional numbers is higher than it is nationally.

The Quebec numbers suggest that pundits who predicted that Stephane Dion's election as Liberal leader would hurt party fortunes in the province were wrong.

"In Quebec, the Liberals continue to look like they're experiencing some upside, based on the selection of Stephane Dion among other things,'' said Decima president Bruce Anderson. "At 27 per cent, that's a pretty good number for them, relative to where they've been.''

He said the Tories may be climbing back from a low of 12 per cent in Quebec recorded in the earlier December survey.

"If we look over time, you'd still come away saying maybe the Conservatives have kind of hit a floor in Quebec, but the Liberals look like they continue to see some strength that certainly wasn't there last year and has survived the selection of Stephane Dion.''

Anderson said the Tories also seem to have overcome the negative fallout from the income-trust decision and regained strength in the West.

But, he added, there are some clear demographic challenges for the party.

Tory support is stronger among men and rural voters. The Liberals are big with women and urbanites.

"For the Liberals to grow, they need to reach out more to men and rural voters and for the Conservatives to grow they need to do better among women and urban voters.

"That's why the social issues matter so much for the Conservatives -- the environment, the position on Afghanistan, to some degree the same-sex marriage debate.''

Anderson also said the data suggest that the NDP are being squeezed between the Liberals, with their new, environmentally friendly leader, and the Green party.

"The Green party, at between five and 10 per cent, is obviously a very significant threat to the NDP.''

As for a spring election, Anderson stressed that it's not up to him to make political judgments for the parties, but he suggested that the outcome would be too close to call, based on the latest data.

"Everybody's got to make their own calculations,'' he said. "If nobody wants to enter an election uncertain of the outcome, then yes, I think these numbers argue caution for everybody.''

The Decima poll surveyed 1,012 people was part of a national omnibus survey. The national results have a margin of error of plus or minus 3.1 percentage points, 19 times out of 20. The margin is higher in provincial percentages because of the smaller numbers of respondents.