While the big-name candidates in the Ontario PC leadership played it safe during the first debate of the contest, they let Tanya Granic Allen steal the show.

Granic Allen put in by far the feistiest performance of the hour-long televised event, taking shots at former leader Patrick Brown, calling out "corruption" in the PC party and showing no fear of jumping into any topic.

"I'm here to be a grassroots voice for... people who are opposed to the Kathleen Wynne sex-ed agenda, pro-lifers, free-speech advocates and other social conservatives," declared Granic Allen as the debate began. In the hour that followed, she more than held her own against Christine Elliott, Doug Ford and Caroline Mulroney, firmly establishing herself as a factor in the race.

It's a sign that social conservatives intend to have an influence over who becomes the next PC leader, and possibly the next premier.

Granic Allen's support base cannot be insignificant: she said she was able to generate the $100,000 entry fee to the contest through donations. She is president of the group Parents As First Educators, which claims 80,000 members. The group describes itself as a "leader in the fight" against a "radical sex-ed curriculum in Ontario."

Ontario Conservative party leadership candidates Tanya Granic Allen, left to right, Christine Elliott, Doug Ford and Caroline Mulroney are seen in TVO studios in Toronto on Thursday, February 15, 2018 following a televised debate. (Chris Young/Canadian Press)

Her candidacy means that sex-ed and other social conservative issues are now high on the agenda among the Progressive Conservatives as the party decides who should lead it into the spring election campaign.

Brown won the 2015 leadership race in part by courting social conservatives, but then tried to steer the party in a different direction. That about-face taught Granic Allen a lesson, she said in a letter to supporters last week, aiming to raise money to run for the leadership.

"When it comes to these leadership contests, we are far better off supporting candidates who we can trust and who will speak out on our issues," she wrote. "We have to make sure the social conservative voice is being respected."

Granic Allen insists she is not a single-issue candidate. But during the debate she kept raising sex ed, even when moderator Steve Paikin tried to steer her toward other aspects of the school system.

Caroline Mulroney supporters gather outside TVO studios in Toronto ahead of the televised debate between the four Ontario PC party leadership candidates. (Chris Young/Canadian Press)

"I have to talk about the sex ed, it's my number one priority," she said.

"What else in education today needs improving that you've got your eye on?" asked Paikin. "Sex ed isn't going to improve math scores, so tell me about something else."

Granic Allen's reply: "Maybe they will focus more on math if they're not talking about anal sex in the classroom."

None of the candidates challenged her directly on that assertion.

Rather, Ford and Elliott agreed that they, too, have problems with the sex-ed reforms.

Ontario PC leadership candidate Doug Ford. (Chris Young/Canadian Press)

"I believe in teaching your kids at home first when it comes to this," said Ford, slamming "the Liberal ideology that's trying to be shoved down our throats with the sex-ed curriculum."

Elliott questioned the "age appropriateness" of some of the curriculum. "Maybe something that children are learning in Grade 2 now, they should learn in Grade 8 or 9 or 10."

She also claimed the curriculum "doesn't cover ... cyberbullying and sexting and all those things related to technology." In fact, both are specifically mentioned in the elementary and secondary health and phys-ed curricula.

Mulroney is the only candidate opposed to scrapping the sex-ed reforms. "I commit to consulting parents on all things that affect families and children, but I am not going to reopen the curriculum," said Mulroney, who identified herself as Roman Catholic during the debate.

Ontario PC leadership candidate Christine Elliott (Chris Young/Canadian Press)

Granic Allen made her presence felt throughout the hour. She dismissed the federal carbon tax as a "cockamamie idea" hatched by Prime Minister Justin Trudeau. She said the PC party's campaign platform, called the People's Guarantee, "died the day Patrick Brown resigned." She wrapped by slamming Ontario's ban on so-called conversion therapy, aimed at changing the sexual orientation or gender identity of young people.

Given the ranked-ballot system the PCs are using, the three big-name candidates will be reluctant to attack Granic Allen: if she is knocked off the ballot first, Mulroney, Ford and Elliott will all hope to be her supporters' number-two choice. And that could drive the Ontario PC party further toward a social conservatism that Patrick Brown rejected.