CHICAGO (CBS) — CBS 2 has learned about a power play in the race for Chicago mayor.

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Three candidates focusing their fire on one target: current Mayor Rahm Emanuel.

CBS 2 political reporter Derrick Blakley explains.

With a simple tweet, Paul Vallas announced he was running for Chicago mayor.

But Vallas, businessman Willie Wilson and former Chicago Police Superintendent Garry McCarthy have already had discussions in concentrating their fire on Mayor Emanuel.

“The bottom line is we agreed that we are going to run a professional policy-based discussion campaign,” says McCarthy. “Not the attack ads that we see from Emanuel.

“We’re not going to be cutting up one another,” says Wilson. “The target is Mayor Rahm Emanuel.

Wilson invited Vallas to his high-rise penthouse home.

“We have to have an open dialog and conversation,” says Wilson.

And he met McCarthy here twice. The second time so that 25 ministers can hear McCarthy’s side of the Laquan McDonald story.

Wilson assisting McCarthy’s campaign.

“I think we’re in unusual circumstances and in unusual times here in Chicago,” says McCarthy. “I told them that a cover-up happened in City Hall.”

Unusual cooperation among competitors aimed at isolating Mayor Emanuel.

“Anything that it takes to get him out,” says Wilson. “I want him out.”

“We want what’s best for Chicago. And I don’t think you can say that about the mayor,” says McCarthy. “He’s a man who makes decisions based on what’s best for himself.”

Vallas is expected to officially announce his entry in the race next week.