Justin Trudeau's Liberals have opened up a six-point lead over the Conservatives, even though the RCMP's stunning allegations about the Senate scandal did not cause sudden major damage to Tory support, a new poll finds.

There is little to brighten the bleak period Prime Minister Stephen Harper's governing party is suffering: The Conservatives are down just one percentage point, but still, that is their lowest level of support since the 2011 election. The survey also indicates opposition may be consolidating under the Liberal banner.

The Ipsos-CTV poll conducted this week shows the Liberals at 35 per cent, the Conservatives at 29 per cent, and the NDP at 26 per cent.

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The most notable change from a month ago is among the opposition parties – and it suggests Canadians who dislike Mr. Harper are shifting to the Liberals rather than to Thomas Mulcair's NDP.

An October Ipsos poll found the two opposition parties statistically tied, with the Liberals at 31 and the New Democrats at 30. Now the Liberals are nine percentage points ahead of the New Democrats.

Darrell Bricker, chief executive officer of Ipsos Global Public Affairs, said the survey indicates that voters most committed to dislodging Mr. Harper are more supportive of the Liberals, suggesting "those who feel most strongly are consolidating under a single option." That is good news for Mr. Trudeau's party – and bad news for both the NDP and Conservatives.

The poll was conducted over a period when the Liberals were gaining credit for performing well in Monday's four by-elections, almost stealing a Conservative Manitoba stronghold, Brandon-Souris. However, opposition support is changeable, and the 2015 election is a long way off.

Mr. Trudeau won the Liberal leadership seven months ago. The NDP will hope his extended honeymoon is only temporary, and that their own overall national support remains strong enough that they are competitive.

But the NDP will not like the snapshot in this poll. In Ontario, Quebec, and B.C., the three biggest provinces, the Liberals now hold a significant lead.

In Ontario, the Liberals, with 37 per cent, have a seven-point lead over the Conservatives at 30 per cent, while the NDP has 29. In Quebec, the Liberals, with 33 per cent, have a six-point edge over both the Bloc Québécois and the NDP, with the Conservatives at only 12 per cent. In B.C., the Liberals, at 37 per cent, are seven points ahead of the NDP at 30 per cent, while the Conservatives have 28 per cent.

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Even though the Conservatives' fall is only slight, it is still bad news for Mr. Harper. Mr. Bricker noted that a couple of significant positive stories – the agreement-in-principle on free trade with the European Union, and Finance Minister Jim Flaherty's projection of a bigger surplus for 2015 – were washed away by the Senate scandal.

The consolation for the Tories is that the survey did not find a sudden collapse after Nov. 20, when RCMP court documents detailed the roles of a dozen senior Conservatives in the Senate controversy and alleged Mr. Harper's former chief of staff, Nigel Wright, committed a crime in connection with it.

However, Mr. Bricker said it does not appear to have dramatically changed Canadians' way of looking at the issue.

He said that he had wondered if this poll would find a "Sheila Fraser moment" had struck Mr. Harper – a sudden collapse like the one that knocked 10 points from the support of Liberal prime minister Paul Martin when auditor-general Fraser reported on the sponsorship scandal in February, 2004.

The Ipsos poll surveyed 1,014 people online, and is considered accurate to within 3.5 percentage points.