Carlos Ramirez-Rosa, a Chicago alderman, described Ms. Lightfoot’s tenure as “chaotic.”

“One of the hallmarks of her approach has been to take things very personal,” he said, “and to engage in combat when, in fact, there is a path toward collaboration.”

She has seen high turnover among key advisers at City Hall, and aides have grumbled about a difficult work environment and a testy mayor who is known to berate subordinates. Despite the city’s mounting problems, Ms. Lightfoot has left crucial administrative positions vacant, including her deputy mayor of public safety, a job that was left unfilled for months until last May.

And last fall, the head of Chicago’s largest police union openly defied Ms. Lightfoot on her order that all city employees report their vaccination status — a conflict that laid bare the tensions between the mayor and rank-and-file officers.