Mayor Rahm Emanuel prepared to introduce 28-year Police Department veteran Eddie Johnson as his choice for interim police superintendent Monday, after rejecting three candidates put forth by the Police Board he appointed. View Full Caption DNAinfo/Justin Breen

CHICAGO — Why did Mayor Rahm Emanuel shockingly nix all the three top cop finalists and ditch his soft-spoken interim police superintendent in exchange for the department’s charismatic, yet inexperienced, chief of patrol Eddie Johnson?

Well, Chicago’s beleaguered boss was fresh out of other options.

As I pointed out last week, the Chicago Police Board's three top cop finalists lacked experience running big city departments. So does Johnson.

RELATED: SHOULD CHICAGO'S NEW TOP COP HAVE MORE BIG CITY EXPERIENCE THAN LAST GUY?

As things turn out, the internal candidate being pushed by the City Council's black caucus, Deputy Supt. Eugene Williams, was tripped up by an investigation into alleged cheating on the department's lieutenant's exam, top city sources told DNAinfo. Williams couldn't be reached for comment but three people, including the wife of a former first deputy superintendent, were allegedly involved in the incident, the sources say.

Emanuel’s interviews with the supposed front-runner, DeKalb County, Ga. public safety director Cedric Alexander, didn’t go that well. Alexander told NBC 5’s Mary Ann Ahern that he was offered the job only to have it rescinded.

But City Hall sources tell me that the suburban public safety director may have misunderstood the mayor’s follow-up questions as a job offer.

What’s shocking to a lot of people is that the mayor tapped Johnson to replace John Escalante as interim police boss.

Well, here’s the backstory on how Johnson got the mayor's attention.

After former police Supt. Garry McCarthy was fired, the mayor’s weekly meetings with Escalante and his three top staffers often left Emanuel’s questions about violence reduction strategies unanswered. The mayor started inviting additional top police brass — including Johnson — to the weekly City Hall sit-downs, sources said.

Emanuel got to know Johnson better during those meetings.

When it became clear to Emanuel early last week that the Police Board finalists weren’t up to snuff, he met with Johnson — who didn’t apply for the top cop job for personal reasons that he will explain at a news conference scheduled for 3 p.m. today — to discuss his interest in replacing Escalante as interim police superintendent, top city sources said.

Despite what the headlines might say, Johnson isn’t a lock for leading the department permanently.

Consider Johnson’s appointment a trial by fire going into a hot summer that many worry could be the most violent in recent history.

Low morale among the rank-and-file who don’t feel Police Department leadership and City Hall have their back has led to a steep decline in police stops. That has emboldened warring gang factions responsible for the city’s spike in shootings that has the city on pace to top 600 murders this year.

The U.S. Justice Department probe of the city’s beleaguered Police Department continues, and there’s a chance that at least some of the federal government’s recommendations will get announced this summer.

Given the Police Department’s morale problem — and the pressure from the City Council's black caucus for the mayor to appoint an African-American insider — there’s a general feeling at City Hall that the best person to deliver the Justice Department edicts to rank-and-file cops is a respected leader within the department.

And Johnson, at least temporarily, can fill that role, top city sources said.

That gives Johnson at least a few months to prove himself while the Police Board goes back to the drawing board to come up with more suitable top cop finalists for the mayor to consider.

If he wants the job, Johnson will have to apply and be fully vetted by the Police Board.

For Emanuel, giving the charismatic chief of patrol a shot was a better option than appointing an insider facing an internal investigation and risk further ticking off rank-and-file cops by appointing another outsider to lead the department.

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