Brown's entry into the leadership race threatens to overshadow his opponents - Toronto lawyer Caroline Mulroney, former Toronto councillor Doug Ford, former Tory legislator Christine Elliott and social conservative activist Tanya Granic Allen.
Brown touted his platform, the "People's Guarantee", which none of the other leadership candidates have endorsed.
Earlier this month an email sent by interim party leader Vic Fedeli to the Tory caucus said the party's membership numbers were not 200,000 as Brown had claimed, but were closer to 133,000.
Hannah Sadovnick, 22, attended Sunday's rally because she's been a staunch supporter of Brown since she heard him speak at an event at Ryerson University previous year.
"Our membership has gone from 12,000, and whether it's 145,000 or 180,000 or 200,000, it's still the largest we have ever been".
"What you and every member should know is that no leader in any political party is involved in the collection of membership fees", he said of Hillier's allegations that $700,000 from party memberships is "missing".
Latif is the party's nominee in the riding of Windsor-Tecumseh. He added he has taken two lie detector tests and "passed both easily".
"What has happened to me, I wouldn't wish on my worst enemy. To be vilified without due process is absolutely gutting", he said.
"The fact that the interim leader made a decision to kick him out of caucus three weeks after all this came and after CTV recanted the most serious allegations of underage girls and drinking.to me indicates that there's a bigger power play going on right now to ensure Patrick Brown is unable to run", Parks said. He will sit as an independent when the legislature resumes on Tuesday.
Brown reiterated that he plans to sue CTV News, though the network has not been served with any lawsuit.
Brown says he has cleared his name, and has received overwhelming support from Ontarians.
"It has been revealed through news stories about my personal finances, that these individuals have illegally gained access to my personal information", he said.
Meanwhile, Fedeli said he wrote to the party executive before Brown joined the leadership race, raising concerns about his suitability as a Tory candidate.