Open this photo in gallery Peter MacKay, who is running for the leadership of the Conservative Party of Canada, said he would 'roll back the Trudeau carbon tax.' BLAIR GABLE/Reuters

The key contenders in the Conservative leadership race say they plan to keep fighting the federal carbon tax, if they win the party’s top job.

While Peter MacKay, Erin O’Toole and Marilyn Gladu have tried to distance themselves from other elements of outgoing leader Andrew Scheer’s election campaign, all confirmed to The Globe and Mail that on the carbon tax they agree with Mr. Scheer. The positions reflect the stark divide between the Conservative base’s opposition to the carbon tax compared with the strong backing it gets from Liberal and NDP supporters.

In a statement, Mr. MacKay said he would “roll back the Trudeau carbon tax.” In a separate statement, Mr. O’Toole said he would “scrap the federal carbon tax and focus on how Canada can become a global leader in zero-carbon technology like nuclear.”

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Neither candidate was available for an interview.

Who’s running for the Conservative Party leadership? The list so far

Carbon pricing in Canada: A guide to who’s affected, who pays what and who opposes it

When Ms. Gladu first floated a leadership bid in December, she said she didn’t think it would be “profitable to try to take away” the carbon tax, noting “Canadians have said that they will accept it.”

Now that she is an official candidate, Ms. Gladu has changed her mind. She told The Globe she believes a carbon tax is “really not an effective way to get a reduction” in emissions.

“I will revoke the federal carbon tax,” she said.

According to the Ecofiscal Commission, an independent group that championed carbon taxes before it closed in 2019, the measure has limited or reduced emissions in jurisdictions such as British Columbia and Sweden.

Ruling out a carbon tax removes a key tool for tackling climate change and comes as Canadians put an increased focus on it. According to a December poll from Nanos Research, more than one-third of Canadians believe the environment should be the top priority in 2020.

After Doug Ford rode to power in Ontario slamming the carbon price, the Conservatives were hoping the same position would help them federally. Instead, more Canadians voted for parties that championed a carbon tax.

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But as Ontario MP Michael Chong learned in his failed 2017 Conservative leadership bid, strong support for carbon pricing stops at the party’s doors. At the time, Mr. Chong was the only candidate to advocate for a carbon tax; in December, Mr. Chong said he didn’t know if he would still back it because the party should respect its members views.

On Wednesday, he ruled out a leadership bid, telling The Globe he concluded, "There’s no path to victory.” He said the next leader needs an “ambitious agenda to deal with our subpar environmental and economic performance.”

But he said that doesn’t have to include a carbon tax, which he called “the most economically efficient way to reduce emissions" but not the only way.

On Wednesday, Manitoba MP Candice Bergen also confirmed she would not make a leadership bid.

Conservative MPs John Williamson and Michelle Rempel Garner are still considering leadership bids.

The carbon tax is the most prominent and contentious part of the Liberal government’s climate plan, but it is just one part of more than 50 measures Ottawa has introduced to reduce Canada’s greenhouse gas emissions. Other policies include regulating methane emissions, incentives for zero-emissions vehicles and investments in green infrastructure and clean technology.

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The policies still leave Canada well short of meeting its 2030 emissions targets; the Liberals have said they will introduce more measures to reach the goal.

The Conservatives will elect their next leader in Toronto on June 27.