Months of pointed questions on the Senate scandal is paying off for NDP Leader Tom Mulcair by bolstering party support and striking a blow to the Conservative brand, according to the latest Nanos Party Power Index.

For the first time, the NDP has scored higher than the Conservatives on the weekly index.

"We can start to see a significant trend emerge that is favouring the New Democrats," Nik Nanos, president and CEO of Nanos Research, told Power & Politics host Evan Solomon.

The index is a combination of measurements of federal party brands based on questions about the parties and the leaders. The score is on a scale of zero to 100 for each party.

The number: 51 The percentage of support for the NDP, the first time the party has pulled ahead of the Conservatives. Source: Nanos Party Power Weekly Index Tracking, four week rolling averages of 1,000 Canadians completed Nov. 30, 2013. Random land- and cell-line sample using live agents. A sample of 1,000 Canadians is accurate 3.1 percentage points, plus or minus 19 times out of 20.

The Liberals remain in the lead with a score of 54, which is a drop of five points from last month. The NDP has gained four points for a score of 51, while the Conservatives have dropped 3 points for a final score of 50.

The results are based on random telephone (cell and land-line) interviews with 1,000 Canadians using a four-week rolling average ending Nov. 11, and is accurate to within 3.1 percentage points, 19 times out of 20.

"For the opposition party, (the Senate scandal) is the gift that keeps on giving, because there are new twists and turns that keep this particular story alive," Nanos said.

Mulcair performance, policy could attract voters

Mulcair is the only federal party leader that has gained favour among Canadians in the past month, on the basis of strong leadership qualities, according to the Nanos Party Power Index.

Mulcair is up 7 points for a score of 51, while Trudeau has dropped 5 points to 52 and Harper has the greatest loss of 7 points for a score of 50.

"Mulcair has clearly benefited from the profile he has in the Senate controversy, his hammering of the Prime Minister day after day," Nanos said.

The NDP leader recently introduced new energy policy, which Nanos believes is a smart way to bring new supporters on board.

"It's not enough for (Mulcair) to just tear down Stephen Harper, he needs to set himself up as a potential counterpoint to both Stephen Harper and an alternative to Justin Trudeau," Nanos said.

Nanos points out that the leader's energy plan is likely phase two of the New Democrats' strategy to form the government after the next election.

"He's putting policy in the New Democratic window to attract voters."

Nik Nanos digs beneath the numbers with CBC News Network's Power & Politics to get to the political, economic and social forces that shape our lives. Recognized as one of Canada's top research experts, Nanos provides numbers-driven counsel to senior executives and major organizations. He leads the analyst team at Nanos, is a Fellow of the Marketing Research and Intelligence Association and a Research Associate Professor with SUNY (Buffalo).