Chicago mayor Rahm Emanuel says he will not seek a third term

CHICAGO, Sept 4 (Reuters) - Chicago Mayor Rahm Emanuel said on Tuesday he will not seek re-election next year, throwing open the top job in the third-largest U.S. city, after facing widespread criticism over his handling of the city's gun violence.

Emanuel, who has been mayor since 2011 and previously served as White House chief of staff to President Barack Obama, was up for a third term and would have faced a crowded field of candidates in February.

About a dozen people have said they will run to be the next mayor, local media reports said, as critics including U.S. President Donald Trump accuse Emanuel of failing to curb violence that has plagued the city's poorest minority neighborhoods.

"This has been the job of a lifetime, but it is not a job for a lifetime," Emanuel told reporters in an emotional announcement at City Hall alongside his wife Amy Rule. With their three children now in college, it was time for a new chapter, Emanuel said without elaborating.

Emanuel, who has taken steps to improve the city's ailing finances, was also facing a possible voter referendum in November to limit Chicago mayors to two terms in office.

"Chicago is better and stronger for his leadership, and I was a better president for his wise counsel at a particularly perilous time for our country," Obama said in a statement.

Emanuel has clashed with Obama's successor, Trump, on various issues, including immigration.

He has also faced criticism from minority community groups on police reform as gun violence raged this summer.

"The collection of these issues has greatly soured his relationship with a core constituency fundamental to his electoral success: the black community," said Jaime Dominguez, an assistant political science professor at Northwestern University.

In 2017, Trump vowed to bring federal help to fight Chicago's crime.

Chicago, a so-called sanctuary city, sued last year after the Trump administration announced it would cut off cities from some grants unless they cooperated with federal immigration authorities.

Under Emanuel, Chicago also joined lawsuits against the Trump administration over the Affordable Care Act, popularly known as Obamacare, methane emissions and the inclusion of citizenship information in the 2020 U.S. Census.

The Chicago mayoral candidate field includes former Chicago police Superintendent Garry McCarthy, whom Emanuel fired following release of a video showing the 2014 fatal police shooting of black teenager Laquan McDonald. Jury selection in the trial of Chicago police officer Jason Van Dyke, accused of shooting McDonald, is set to begin on Wednesday.

Mayoral challengers also include Paul Vallas, the former chief executive of Chicago Public Schools, and Lori Lightfoot, who served as Chicago Police Board president.

The campaign committee of Emanuel, who also served three terms in the U.S. House of Representatives and was a senior adviser to President Bill Clinton, had $7.56 million in its coffers as of June 30, according to a quarterly filing with the Illinois State Board of Elections.

(Reporting by Suzannah Gonzales and Karen Pierog in Chicago Editing by Caroline Stauffer, Susan Thomas and Bill Berkrot)