Chicago Mayor Richard M Daley has announced he will not run for re-election, ending a political dynasty in which a Daley has reigned over the third-largest US city for much of the past half century.
Mr Daley's decision not to seek a seventh term in February has prompted interest from Chicagoan Rahm Emanuel, President Barack Obama's Chief of Staff.
Mr Daley, 68, a former state legislator and county prosecutor who was reared to assume the political mantle worn by his father, Richard J Daley, from 1955 to 1976, said he had thought about the decision for months.
'I have given it my all. I have done my best,' he said. 'It just feels right.'
A Democrat who like his father never sought higher office after being elected mayor in a special election in 1989, Mr Daley will surpass the 21-year tenure in office of his famous father in December.
Mr Daley's decision came as a surprise, and will leave a gaping hole in Chicago's leadership, where a member of the Irish American Daley family has been mayor for 42 out of the past 55 years.
The list of potential successors, beyond an array of local aldermen and politicians, includes Mr Emanuel, a former US congressman who has said he would consider running for mayor after Mr Daley left the scene.
Mr Emanuel issued a statement saying he was 'surprised' by Mr Daley's announcement, adding, 'I have never been surprised by his leadership, dedication and tireless work on behalf of the city and the people of Chicago.'
If Mr Emanuel were to jump into the race, he would have to act quickly. Mr Daley's announcement came just two-and-a-half months before the 22 November deadline for filing paperwork to run and only five months before the election. That timetable will likely feed a scramble for fund-raising and political support.
'It's not at all clear whether Rahm can break loose fast enough to get back here,' said Dick Simpson, a political analyst at the University of Illinois at Chicago.
Mr Obama, himself a Chicagoan, also lauded Mr Daley, saying in a statement, 'he helped build Chicago's image as a world class city and leaves a legacy of progress that will be appreciated for generations to come.'
On a personal level, Mr Daley's wife, Maggie, has been treated in recent years for cancer that has spread. She stood next to her husband, with the aid of a crutch, during a news conference at City Hall at which he took no questions.
After more than two decades in City Hall, Mr Daley leaves a long legacy - although he has had his share of detractors.
'He'll be remembered positively for shepherding Chicago through the transformation from a manufacturing and service economy to becoming a global city,' Mr Simpson said.
Mr Daley cast himself as an urban planner intent on beautifying the city of 3m as it emerged from its grimy industrial past of steel mills and slaughterhouses.
He pushed hard for Chicago's bid to host the 2016 Olympic Games but was disappointed when the effort failed, and he has come under increasing criticism on several fronts.
His public approval rating sank to about one-third of respondents in a Chicago Tribune poll a few months ago.
