Explains Kennedy, "The mayor has the right background and right outlook to redirect city government. There is a core of people around the top of the Police Department who know what needs to be done, and they are finally in a position to do it. And bringing Susan Lee into the equation is something that could be transformative in itself."

Chicago is not Los Angeles, however, and Lee's complex plans will face the city's unique obstacles. She notes that, as in L.A., progress will take time, certainly years, and no shortage of sustained political will and financial resources to produce lasting results.

Signs of trouble already have surfaced, and some are withholding their judgment on the mayor's full commitment.

Lightfoot has joined Chicago Police Superintendent Eddie Johnson in complaining that judges are too lenient on gun-crime suspects, blaming their release for more violence. The mayor has clashed with the police union, alleging it isn't fully on board with reform. And some community activists don't trust the mayor, remembering her time on the police board, which they criticized as too lenient on problem officers.

The biggest challenge will be money and where City Hall gets the many millions of dollars gun violence experts say is needed to sustain a comprehensive campaign. In an interview, Lee says she found the previous lack of resources devoted to violence reduction in Chicago "astounding." But the new mayor also is grappling with enormous budget and pension crises.

Getty Images Chicago police officers collect evidence at the scene of a fatal shooting in Englewood last October.

Others worry that resources and focus could be diverted as a result of the city's no-holds-barred politics.

"All of these cities have had infighting, but there's nothing like Chicago's infighting," warns Gary Slutkin, a physician who founded Cure Violence, an intervention organization that expanded internationally after launching in Chicago in 2000 and that promotes fighting violence as if it's an epidemic. "I mean, within groups, between groups, within government—the level of infighting is a culture in Chicago."

Chicago's violence goes back generations, and the number of killings in recent years actually has fallen far from the 1990s, when it was common for Chicago to endure more than 900 homicides per year. Still, as homicide deaths dropped elsewhere, Chicago saw them spike to more than 770 as recently as 2016. Last year, the number fell to 561, but even that is more than New York and L.A. combined.

The city's violence is relentless: It subsides, but always erupts again.

This year, the most violent summer weekends have had upward of 70 shootings. A few other cities, such as St. Louis and Baltimore, have higher rates of violence amid smaller populations. But Chicago, with its massive scope and spotlight, stubbornly wears a worldwide reputation as the capital of the country's urban violence and has become a football to kick around for national politicians.