OTTAWA - Justin Trudeau would take the Liberals off life-support and make the sad-sack party a contender if he were leader, according to a new poll that also shows the NDP and Conservatives in a dead heat.

The Abacus Data survey says the front-runners each have the support of 35% of respondents followed by the Liberals at 20%.

Conducted June 20-23, the survey comes at the same time the Conservatives debuted an ad online that attacks NDP Leader Thomas Mulcair for "risky economic theories," including calling "strong growth in some industries a disease."

Mulcair has come under fire for suggesting the boom in the energy sector is harming the manufacturing sector and artificially inflating the value of the dollar.

The 30-second TV spot says Mulcair's opposition to trade agreements is "dangerous" to the economy and that an NDP carbon tax would increase the price of gas, groceries and hydro.

While Trudeau mulls a run for leadership, the poll asked respondents how they would vote if he was leader. Thirty-three percent said Conservative, 32% Liberal and 24% NDP.

David Coletto, CEO of Abacus, said much of the hypothetical gains under Trudeau would come from New Democrats.

The online survey of 1,008 Canadians found that 28% of respondents who back the NDP today would switch and vote Liberal if the Montreal MP were at the helm. Nine percent of Tory supporters would switch while 10% of Liberal supporters would vote for another party if Trudeau was crowned.

A Trudeau leadership would also attract voters aged 60 and over - a group that tends to be more Conservative. Liberals and Conservatives would be tied with 36% of decided voters in that age category.

In battleground Ontario, Liberals would jump to 39% followed by the Conservatives at 34%. And more women (37%) would gravitate to a Trudeau-led party compared with the Tories (29%).

The poll, conducted for QMI Agency, has a margin of error of 3.1 percentage points, 19 times out of 20.