Alberta Premier Jason Kenney has endorsed Erin O’Toole for the Conservative Party’s next leader.

The endorsement from a prominent Western Conservative is significant in a race that features no well-known contenders west of Ontario.

“We need a leader who is competent and principled,” Mr. Kenney wrote in an e-mail to all Conservative party members Thursday announcing his support for Mr. O’Toole.

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“A leader who won’t run away from conservative principles under pressure from the media or the Left.”

In the e-mail, Mr. Kenney stressed the need for the Conservatives’ next leader to unite the party, speak French, win in suburban Ontario and “fight for a fair deal for Western Canada.”

“I know that we can rely on Erin to be that strong leader,” Mr. Kenney wrote.

Mr. O’Toole has represented the Greater Toronto Area riding of Durham since 2012. He is one of eight people running to replace Conservative Leader Andrew Scheer and is considered a front-runner, along with former cabinet minister Peter MacKay.

When both Mr. O’Toole and Mr. MacKay were already in the leadership race, Mr. Kenney was still lobbying for others to run. He first urged former interim leader Rona Ambrose to jump in and, when she declined, he publicly advocated for former cabinet minister John Baird to run.

Mr. Kenney worked alongside Mr. MacKay in cabinet from 2008 to 2015. Mr. O’Toole joined them in cabinet in 2015.

In his e-mail to party members, Mr. Kenney took direct aim at Mr. MacKay as he explained why he was supporting Mr. O’Toole.

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“No one will have their deeply held beliefs dismissed as ‘stinking albatrosses’ under Erin O’Toole’s leadership,” Mr. Kenney wrote – a nod to comments made by Mr. MacKay about the negative impact social-conservative issues had on Mr. Scheer during the fall election campaign.

“The Conservative Party of Canada must choose a Leader who is true blue,” Mr. Kenney said.

Mr. Kenney isn’t just lending his name to the candidate, he’s also encouraging a vast network of organizers and supporters across the country to join the team, according to a source with Mr. O’Toole’s campaign, whom The Globe is not identifying so they could speak about internal matters.

Mr. Kenney hails from the Prairies, but has spent years building up the Conservative base in urban centres and in multicultural communities across Canada.

In a statement, Mr. MacKay’s spokeswoman, Julie Vaux, said “he respects the Premier’s choice.”

“As the next Prime Minister, he will work with Premier Kenney and every other Premier across this country, regardless of who they endorse. He made it very clear this week in Alberta that he would fight for the interests of Albertans," Ms. Vaux said.

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On Wednesday, Mr. MacKay announced that he had raised $1-million in the first six weeks of his campaign. So far, of the eight candidates, only Mr. MacKay and Mr. O’Toole have met the requirements to secure a spot on the final ballot. The others have until March 25 to raise $300,000 and collect 3,000 signatures. Conservatives will elect their new leader on June 27.

Speaking to The Globe at an event in Calgary earlier this week, Mr. MacKay had said he was hoping to meet with the Alberta Premier while in the province this week.

“I worked with Jason for a long time,” Mr. MacKay said. “He and I go back a long way.”

On Wednesday, Mr. Kenney’s office only said according to his calendar, the Premier was not meeting with Mr. MacKay.

With a report from Kelly Cryderman