She has received 25 endorsements from presidents of riding associations across the province, while Wynne has received only 14.
The two women are far and away the front runners heading into the leadership convention, which will be held in Toronto later this month.
Pupatello, 50, has frequently made a point of claiming that, if she becomes premier, she can win back rural seats for the Liberal Party because she's from Windsor, while her five opponents are all from Toronto or its surrounding areas.
"Even at our lowest ebb as a party and a government, we're still winning the Toronto seats ... and that fact alone is why so many of my colleagues called and asked me to get into this race, because we have to win outside of Toronto," Pupatello said in a recent interview with The Canadian Press.
"Ultimately I believe that we can win those seats back, where you have to get the NDP to vote for you and you have to get red Tories to vote for you, and I did that for a living for 16 years."
As the former MPP for Windsor West, Pupatello was deputy leader of the Liberals when they were in opposition, and she served in several cabinet positions after they were elected to power in 2003.
She decided not to run again in 2011, instead taking a job with the international professional-services company PricewaterhouseCoopers in Toronto.
Pupatello said recently she was joining the race to be premier because a lot of people urged her to do it.
"Totally non-political people were saying I had to do this, they were calling from all of the sectors where I had worked with them as a [cabinet] minister," she said.
"I'm the jobs guy, and people in my party know me best in that role because I was there the longest ... and it also happens to be what the number one issue is across this province," Pupatello said.
Since falling to a minority position in the legislature in the last provincial election, the Liberals have dealt with a number of controversies, including a police probe of the Ornge air-ambulance service, and a bitter feud with teachers.
"The reason that I'm in [the leadership race] is exactly because of this year, and I think that really is the difference perhaps between me and my colleagues, because I wasn't in the house, because I understand it's a really difficult time for my party and for our government," Pupatello said.
"I want to bring the experience that I've had being on the outside for the past year and a half, and seeing the government with a different set of eyes."
Heading into the convention, Pupatello has the most committed, first-ballot delegate support, as well as the most endorsements from her former caucus and cabinet colleagues.
If she becomes the next premier, Pupatello said she knows that she will be taking on a tough job.
"Inside the party, everywhere we go, we are getting a very warm reception, which is how you know it's really unlike the general public right now," she said.
"We've got a lot of making up to do on a number of fronts before the public wants to trust us with their taxpayers' money."
While Pupatello does not currently have a seat in the legislature, she intends to quickly seek one if elected as the next Liberal leader.
Finance Minister Dwight Duncan is willing to resign from his seat in Windsor-Tecumseh, to give her the opportunity to run in the riding.