Conservative Party of Canada leader Stephen Harper greets supporters after emerging from the locker rooms of a hockey arena during the federal election campaign in Conception Bay South, Newfoundland, April 21, 2011. REUTERS/Greg Locke

TORONTO (Reuters) - The Conservative Party holds a wide lead over rivals heading into the May 2 election, although the New Democrats have gained support, according to a poll released on Friday.

The Nanos Research tracking poll of results for three days of surveys put support for the Conservatives at 37.8 percent, down from 39 percent on Thursday.

Support for the Liberals fell to 26.1 percent from 26.7 percent on Thursday.

The big gainer in the latest poll is the New Democratic Party with 23.7 percent of the vote, up from 22.1 percent a day earlier.

Nanos said NDP support has moved up for the third straight night and that factoring in the margin of error, the Liberals and NDP are now statistically tied.

The New Democratic Party has exploded from an also-ran in Canada’s election campaign to a potential spoiler that could change the Canadian balance of power.

Under Canada’s electoral system, a party needs about 40 percent of the vote to win a majority of the 308 seats in the House of Commons. But a majority also is possible if the gap between the front-runners is more than 10 percentage points.

The Conservatives had a minority in the last Parliament and needed support from at least one other party to stay in power.

The daily Nanos tracking figures are based on a three-day rolling telephone sample of 995 decided voters and are considered accurate within 3.1 percentage points 19 times out of 20.