Shortly after winning the 2022 Conservative leadership race, Pierre Poilievre sought Brian Mulroney’s political counsel over an intimate dinner at Stornoway. The move seemed to signal the new Tory Leader’s willingness to reach out to moderates in the party who had supported Jean Charest in the leadership contest.

During the campaign, Mr. Charest, a former Liberal Quebec premier and federal Progressive Conservative cabinet minister under Mr. Mulroney, had faced charges from Mr. Poilievre that he was a Conservative in name only. No one doubted that Mr. Charest had been the preferred leadership candidate of Mr. Mulroney, his political mentor since 1984.

The former Tory prime minister, who had won a record-size majority government (in terms of seats) in that year’s federal election, saw the overture from Mr. Poilievre as a promising sign.

“As Churchill said, ‘In victory, magnanimity,’” Mr. Mulroney told The Globe and Mail’s Ian Bailey at the time. “If you have a leader who reaches out to his opponents, people who didn’t support him in the party, bringing them together to focus on winning the next election, then you’ve got the right leader, and he has the right attitude.”

Canada’s 18th prime minister, who built a big-tent Tory coalition and twice swept Quebec, also offered this advice to Mr. Poilievre: “I told him you have to fish where the fish are… You can only win elections in Canada from the centre.”

All of Canada now knows what Mr. Poilievre did with that advice. Not only did he sideline the moderates in his own caucus who had supported Mr. Charest, he tacked radically to the right by embracing populist conspiracy theories about the World Economic Forum and vaccine mandates. He denigrated journalists and anyone who disagreed with him. In December, he sat down for a 90-minute YouTube chat with Jordan Peterson, a polarizing culture warrior, during which he denounced Justin Trudeau’s “authoritarian socialism.”

Two days after that was posted in January, Mr. Trudeau announced his resignation. It soon became clear that much of the Conservative lead in the polls stemmed more from the former Liberal prime minister’s unpopularity than anything Mr. Poilievre had been going on about for the previous two years. Once U.S. President Donald Trump began singling out this country for trade punishment and threatening it with 51st-state status, Mr. Poilievre’s Canada-is-broken schtick fell flat.

In all fairness to the Tory Leader, he was not wrong to emphasize affordability issues and the failure of Mr. Trudeau’s Liberals to address the country’s competitiveness and productivity deficits. Nor did he err in identifying the consumer carbon tax as a major irritant for voters after a post-pandemic spike in inflation.

But he was outmanoeuvred by Prime Minister Mark Carney’s surprisingly adroit – for a political rookie – move to axe the tax. As the hated tax came off prices at the pumps on April 1, Liberal MPs posted pictures of themselves at gas stations taking credit for making life more affordable for Canadians. Liberal shamelessness knows no bounds.

Still, Mr. Poilievre should have seen it coming and pivoted to the centre well before Mr. Carney beat him to it. His populist base is still behind him – witness the big crowds at his rallies – but most Canadians, especially those older than 55, do not consider him in the same league as Mr. Carney.

Mr. Poilievre did get a boost this week with an endorsement from Ontario Treasury Board President Caroline Mulroney, a move that surprised some Tories given that her boss, Doug Ford, has patently refused to endorse him and said his MPPs would be too “swamped” to help their federal cousins on the campaign. In introducing Mr. Poilievre at an event on Bay Street, Ms. Mulroney insisted: “I believe, just as my father did, that Pierre Poilievre is ready to lead us to a stronger, a more united and a more prosperous Canada than the one we inherited.”

Shortly before Mr. Poilievre won the Tory leadership, Brian Mulroney told a Laval University audience that he no longer identified much with the modern Conservative Party. Yet, anyone who knew him well does not doubt that Mr. Mulroney would still have voted Conservative on April 28. He had always been fiercely loyal to his own party and believed deeply that Canada needed a strong and credible alternative to the Liberals.

Uninterrupted Liberal rule, Mr. Mulroney believed, was bad for Canada. The country’s “natural governing party,” as it likes to call itself, is prone to arrogance and inertia. Mr. Mulroney showed that a centrist Tory government could take the nation-building leaps that the risk-averse Liberals avoided. He brought free trade and tax reform, and strived to heal the Canada-Quebec divide and Western alienation. He remains the only Tory PM since John A. Macdonald to have won back-to-back majorities.

Mr. Poilievre should have taken his advice in 2022.