A socially conservative 19-year-old university student has won a nomination to run for the Progressive Conservatives in an upcoming Ontario by-election, dealing a blow to Leader Patrick Brown and threatening to tear open divisions in the party over the sexual-education curriculum and abortion.

Sam Oosterhoff defeated party president Rick Dykstra – a friend and political ally of Mr. Brown – and two other candidates Saturday to carry the party banner in Niagara West-Glanbrook.

Mr. Oosterhoff, a first-year political science student at Brock University, campaigned as a "strong family values" candidate. He took aim at both the Liberals' new sex-ed curriculum and a bill to make it easier for same-sex couples to have children using surrogates.

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"I will never waver in my support of parents as primary educators, and I will strive to ensure that parental rights are respected in education," he wrote on his campaign website. In another posting, he urged supporters to target Bill 28, a piece of legislation meant to close a legal loophole that obliged some same-sex couples and other parents using surrogates to adopt their own children.

The PCs are struggling with the role of social conservatives in the party.

During a summer by-election in Scarborough-Rouge River, Mr. Brown's office distributed a leaflet under his signature pledging to "scrap" sex-ed. When media got hold of the missive, Mr. Brown claimed not to have seen it before it was published.

In an effort to douse the firestorm, he declared himself in favour of sex-ed and engaged in a war of words with evangelical and anti-abortion leaders whose support he had previously courted.

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A Tory safe seat, Niagara West-Glanbrook covers a swath of wine country between Hamilton and St. Catharines.

The seat was vacated by former leader Tim Hudak last month. The Liberals have nominated lawyer Vicky Ringuette and the NDP has put forward former Hamilton police union president Mike Thomas.

Mr. Oosterhoff's campaign said Monday he was "not available for interviews" any time this week.

His website says he was raised on a farm and worked at an excavation company before landing a job as an aide to Calgary MP Tom Kmiec last year.

Mike Williscraft, a Grimsby newspaper owner who also ran for the nomination, said Mr. Oosterhoff "worked very hard" to sign up new party members, particularly among conservative churchgoers in the area's large Dutch community.

"I know from speaking to him during the campaign that a significant part of his support was motivated by the abortion issue … that's part of their church's belief," he said.

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Mr. Oosterhoff also benefited from a ranked-ballot system and a divide among the party establishment. While Mr. Brown is close with Mr. Dykstra, both Mr. Williscraft and another candidate, local Councillor Tony Quirk, claimed the support of Mr. Hudak.

Before the vote, Mr. Quirk says, he and Mr. Oosterhoff agreed to encourage their supporters to make each other their second choice. After Mr. Quirk and Mr. Williscraft dropped off the ballot in the first two rounds of counting, Mr. Oosterhoff edged Mr. Dykstra 699 votes to 525.

Mr. Quirk acknowledged he and Mr. Dykstra likely hurt each other's campaigns.

"Did we end up taking votes away from each other and allowing someone else to come up the middle? Maybe. Maybe we should have had a better conversation and better discussion about what would be in the best interest of the party beforehand," he said on Monday.

The flare-up offers some relief for Premier Kathleen Wynne and her unpopular Liberals. A poll last week showed her approval rating at 14 per cent, the lowest-ever for an Ontario premier in a Forum poll. "There will be a clear distinction between the ideas of this young man and the ideas of our candidate," she said. Asked whether she is still planning to lead the Liberals into the 2018 election, Ms. Wynne replied, "I am, I am."

PCs at Queen's Park tried to put a brave face on the result. Moderate MPP Vic Fedeli insisted that, whatever Mr. Oosterhoff's views, he would have to fall in line with the party's support for the sex-ed curriculum. "Our party has been very clear on our position and you're going to see our caucus continue to stand united. And that includes all members of our caucus," he said.