Both the Conservatives' and the NDP's popularity have waned since the federal election in May, while Liberal support has risen, a new Nanos poll for CTV and The Globe and Mail suggests.

The Tories' support from potential voters has dipped to 36.2 per cent, while the NDP and the Liberals are statistically tied, at 26.8 per cent and 27 per cent, respectively.

While the NDP's support in Quebec remains strong, it appears to have weakened after party leader Jack Layton took a leave of absence to undergo treatment for a new cancer.

NDP support in Quebec sits at 34.2 per cent. The NDP took nearly 42 per cent of the popular vote in Quebec during May's federal election.

Pollster Nik Nanos says Layton's absence hurts the NDP in Quebec, because of his personal popularity there.

"What we are seeing . . . is a possible negative wake for the New Democrats with (Layton's) announcement," he said. "We are seeing the Liberals' numbers moving up as a result.

"If we rewind to the last election, in Quebec, it was about Jack Layton, his charisma, his policy and his charm. He really swept the province as a result. Quebec is going to be a key region to watch in terms of those NDP numbers . . . as a result of Jack Layton not being active."

The Liberals poll numbers are better than they were in the recent federal election, but Nanos says that may not be because of a change in leadership.

"This is more of the Liberals being a parking space (for voters)," Nanos said, suggesting the Conservatives focus on ideological issues like crime and the gun control registry could be driving voters to the Liberals.

While the Liberals' fortunes have risen under his leadership, Bob Rae appears to have little to brag about personally as he ranks far below both Layton and Harper on the Nanos Leadership Index.

The index ranks leaders on the issues of trust, vision for Canada and competence.

Layton has a leadership ranking of 88.5, Harper trails closely behind at 86.9 and Rae ranks a mere 25.6.

The Nanos survey was a national random telephone survey of 1,203 Canadians 18 years of age and older. It was completed between July 25 and August 2, 2011.

The statistics of a random sample of 1,203 respondents are accurate to within 2.8 percentage points, plus or minus, 19 times out of 20. For 1015 committed voters, it is accurate to within 3.1 percentage points, plus or minus, 19 times out of 20.