Conservative Leader Stephen Harper and Liberal Leader Justin Trudeau remain locked in a statistical tie in the weekly preferred Prime Minister tracking by Nanos.

Thirty-one per cent of Canadians identified Harper as their choice for preferred PM, while 30 per cent picked Trudeau. NDP Leader Thomas Mulcair remains in third at 19 per cent, followed by Elizabeth May at 4 per cent. Fifteen per cent were unsure.

On the Nanos Party Power Index itself, the federal Liberals are at 57 points out of 100 followed by the Conservatives at 52 points, the NDP at 50 points, the Green Party at 32 points and the BQ at 28 points (QC only).

The Nanos Party Power Index methodology is comprised of a basket of political goods that includes ballot preferences, accessible voters, preferred PM views and evaluations of the leaders. It is modeled similar to a standard confidence index.

Voter accessibility remains a key driver of Liberal strength on the Nanos Party Power Index as they are the only federal party more than half of Canadians would consider voting for.

Asked a series of independent questions for each federal party, 55 per cent of Canadians would consider voting Liberal, 45 per cent would consider voting NDP, 44 per cent would consider voting Conservative, and 30 per cent would consider voting for the Greens.