At the same council meeting where Rob Ford cast the vote that led to his highly anticipated court appearance Wednesday, the mayor's brother rose to say sorry to a left-wing activist named Adam Chaleff-Freudenthaler.

But Doug Ford was not apologizing happily, or voluntarily.

Mr. Chaleff-Freudenthaler had successfully pursued an audit of the mayor's campaign finances, which prompted Councillor Ford to confront him and warn – "what goes around comes around."

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The councillor told reporters before issuing his apology that it was "horseshit" that Toronto's integrity commission had ordered him to publicly say sorry for threatening the 27-year-old.

The very fact that Mr. Chaleff-Freudenthaler knew how to file a complaint to the integrity commissioner over the comment is among the reasons he has become one of Mayor Ford's most daunting opponents. Mr. Chaleff-Freudenthaler and a small circle of his progressive acolytes are the forces behind a conflict-of-interest lawsuit that could push Mr. Ford out of office and an ongoing campaign-finance audit that could cause him nearly as much trouble.

While the mayor's more prominent foes are busy trying to beat him in the court of public opinion, Mr. Chaleff-Freudenthaler, his allies and a handful of pro-bono lawyers are out to beat the mayor in a court of law.

The most public test yet of their strategy will begin Wednesday, when Mr. Ford is scheduled to take the stand to answer allegations that he broke the Municipal Conflict of Interest Act when, on Feb. 7, he voted to let himself off the hook for failing to personally repay $3,150 in improper donations to his football foundation.

The plaintiff in that lawsuit is Paul Magder, a politically engaged businessman who has formally complained about a Ford brother before.

Mr. Magder filed a complaint to the integrity commissioner last year about Councillor Doug Ford's attempts to overhaul the Port Lands plan.

But it was Mr. Chaleff-Freudenthaler who helped steer Mr. Magder toward Clayton Ruby, the prominent human-rights lawyer spearheading the conflict-of-interest case.

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Mr. Magder, whose children went to school with Mr. Chaleff-Freudenthaler, became a family friend and, ultimately, a volunteer on Mr. Chaleff-Freudenthaler's failed run at a seat on the public school board in 2010.

When Mr. Ford underwent a closed-door cross-examination for the case June 28, it was not Mr. Magder who sat in to observe – it was lawyer Max Reed, a friend of Mr. Chaleff-Freudenthaler's from their university days in Montreal and his partner in launching a campaign finance audit against the mayor.

Both are members of a group called Fair Elections Toronto, which petitioned for at least eight other campaign-finance audits against councillors, most of whom are allies of the mayor.

Mr. Reed also worked on policy and communications for David Miller's 2006 re-election campaign.

A long-time labour organizer, NDP stalwart, and former vice-chair of the Toronto Public Library Board, Mr. Chaleff-Freudenthaler cut his teeth fighting Mike Harris's Progressive Conservative government.

His work earned him a spot on Now Magazine's 2003 list of top teen activists and artists to watch, alongside a then little-known actress named Ellen Page.

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Now his involvement in the legal challenges has the mayor's allies dismissing the cases as the last refuge of a handful of "sore losers" who despise Mr. Ford's politics.

"Adam [Chaleff-Freudenthaler] never accepted the results of the last election," Councillor Denzil Minnan-Wong said. "His actions have demonstrated he's never accepted it. What he and his group are trying to do is change the democratic choice of Toronto's voters."

But others, including potential mayoral candidate Adam Vaughan, say the full court press against Mr. Ford is simply an instance of the mayor reaping what he has sown.

"I think the mayor operates in a way that he thinks the rules are for everybody else and that they don't apply to him," Mr. Vaughan said. "When you do that, you're bound to upset people who are as defiantly principled as someone like Adam is."

Mr. Reed and Mr. Chaleff-Freudenthaler declined to be interviewed for this story, citing the pending legal cases. Attempts to reach Mr. Magder through his lawyer were unsuccessful.