In a room on the Northwest Side filled with “Garry McCarthy for Mayor” signs, Chicago’s fired former top cop warned anyone who thinks he’s not serious to “wait a couple of weeks, and let’s just see how fake my candidacy is.”

He also brushed off a protest by about 15 members of SEIU Local 1 outside his fundraiser Sunday at the Irish American Heritage Center as a game of “look at the squirrel” — a strategy he expects his political opponents to repeat.

The SEIU members, including one in a Donald Trump outfit, marched outside the fundraiser and handed out copies of a Chicago Sun-Times article tying McCarthy’s possible run for mayor to a lucrative O’Hare janitorial contract up for re-bidding.

“The theory is that I’m running a fake campaign so that somebody else can get a contract,” McCarthy said in his speech. “Now that makes great sense to me.”

Though McCarthy stopped just short of announcing his campaign Sunday, that announcement was all that seemed to be missing from the tightly controlled event attended by some members of the 1985 Chicago Bears. “McCarthy For Mayor” banners hung in the building’s lobby and Main Hall. And in his speech, McCarthy sounded like a man who had made up his mind.

“What I will offer Chicago is performance-based government,” McCarthy said.

Jerry Morrison, assistant to the president of SEIU Local 1, has charged that McCarthy’s threat to challenge Rahm Emanuel for the mayor’s office is little more than a “crass attempt” to bully the mayor into renewing a five-year, $107 million O’Hare janitorial contract with United Maintenance.

The company is owned by Rick Simon, McCarthy’s friend and former business associate. SEIU Local 1 is part of a group of unions that now owns the Chicago Sun-Times.

Last week, McCarthy said he could care less about the protest outside his $100-a-ticket fundraiser.

“The whole thing is nonsense. It’s completely made up. I’m not gonna talk about it. . . . I’m not gonna play this stupid Chicago game,” he said.