Former cabinet minister Steven Del Duca is on the verge of becoming the new leader of the Ontario Liberals, as delegates gather this weekend for the party's convention to choose a candidate to take on Premier Doug Ford.

Del Duca has sewn up more than half of the elected delegates slated to attend the convention in Mississauga, giving him a strong shot at winning the leadership on the first ballot.

Under the Liberal party's own rules, elected delegates who are aligned to specific candidates cannot vote for anyone else on the first ballot. To control this, those delegates receive a ballot pre-marked with only the name of their leadership candidate.

Del Duca, who served as transportation minister in the Kathleen Wynne government, obtained the backing of 1,171 of the 2,084 delegates chosen by party members last month.

For Del Duca, only two real questions remain: how many of his delegates make it to the convention to vote? How many of the roughly 540 additional Liberals eligible to attend as uncommitted delegates bother to show up and vote for anyone other than Del Duca?

The candidates for the Ontario Liberal leadership, from left: Alvin Tedjo, Mitzie Hunter, Kate Graham, Brenda Hollingsworth, Steven Del Duca and Michael Coteau. (Angela Gemmill/CBC)

Observers inside and outside Del Duca's team attribute his dominance in the leadership race to a combination of work ethic, on-the-ground recruitment, and hiring two talented organizers, Tom Allison and Milton Chan, to run his campaign.

"Steven was better organized and he better understood how to get as many delegates elected as possible," said Dan Moulton, a former Liberal staffer, now a vice president with Crestview Strategy, a Toronto-based communications and government relations firm.

"What we've seen is a lot of hard work and a lot of time invested in securing a very strong position running into this weekend," Moulton said in an interview. "I'm not sure the other campaigns had the same skill set in ensuring they had a robust slate of candidates running in every single riding."

Don Valley East MPP Michael Coteau is sitting a distant second, capturing less than one third of Del Duca's elected delegate numbers.

"Some would have you believe that the Ontario Liberal Leadership race is over. They're wrong," Coteau said in a statement last month.

"I'm going to do everything I can to represent the voices of people across the Ontario Liberal Party who are calling for change," Coteau said. He urged his 371 delegates to come to the convention and promised he will "be there until the last ballot is counted."

Kate Graham, now seeking the Ontario Liberal leadership, ran unsuccessfully in the 2018 provincial election as the party's candidate in London North Centre. (Colin Butler/CBC News)

Kate Graham, who has never held elected office, is the surprise third-place candidate going into the convention, with 273 delegates. Her chief boost came from former deputy premier Deb Matthews, a key architect of Wynne's leadership victory in 2013.

"It's not over till it's over," Graham told CBC's London Morning this week. "We're going to go [to the convention] and make our pitch."

Others are implicitly conceding defeat by already talking about the importance of party unity.

"Whoever wins the leadership race this weekend, it is about unifying the party," Scarborough MPP Mitzie Hunter said in a tweet this week. "We have to focus on getting ready for the 2022 election because we cannot afford another four years of Doug Ford in this province."

Hunter has 130 delegates. The two candidates sitting in fifth and six place, Alvin Tedjo and Brenda Hollingsworth, captured fewer than 100 delegates between them.

The first ballot voting runs all day Friday, and the convention officially opens Friday evening with a tribute to Wynne. Candidate speeches take place Saturday morning, and the party expects to announce the results of the first ballot at around 1:45 p.m.