With key endorsements from SEIU Local 1 and former White House Senior Adviser Valerie Jarrett, Cook County Board President Toni Preckwinkle announced her run for mayor Thursday at the same spot where Harold Washington and Barack Obama announced their historic bids for office.

“There are those who have asked or will ask why I would want to take on this job,” Preckwinkle said. “I understand their thinking. I face no shortage of challenges while in public office, why would I want to tackle even more? I’m doing this because I can, I’m doing this because it’s necessary. I don’t make this decision lightly.”

She was joined by Ken Bennett, a former aide to Mayor Rahm Emanuel, women’s organizer Rebecca Sive, anti-violence advocate Floyd Stanford and a handful of county board members for the roughly 40-minute announcement at the Chicago Lake Shore Hotel.

Also present at the announcement at the Chicago Lake Shore Hotel was a representative with SEIU Local 1, which is part of a group of unions that owns the Chicago Sun-Times.

The spot in East Hyde Park overlooking the lake is where Obama first announced his 1996 bid for the Illinois senate and where Washington, the city’s first black mayor, announced his bid for the city’s top office in 1982.

If elected, Preckwinkle would be the first black woman to lead Chicago.

Preckwinkle and those who joined her pointed to her background as a teacher and her reforms to the county’s jail and hospital system as just a few of her qualifications.

Bennett, the father of Chance the Rapper, said the city deserves a mayor who will “fight” for an equitable school system, economic development and jobs in all of the city’s 77 community areas and a comprehensive public safety plan.

Preckwinkle talked about the need for economic investment throughout the city — not just downtown. She also talked about the need for an elected school board and better schools, more police accountability and addressing the city’s gun violence by tackling its root causes instead of relying on incarcerating people.

With Emanuel not seeking a third term, Preckwinkle becomes a likely front-runner in the race.

A former five-term alderman of the fourth ward, Preckwinkle was elected board president in 2010.

Earlier this year, Preckwinkle won a third term, defeating former Ald. Bob Fioretti, and became the boss of Cook County Democratic Party after Cook County Assessor Joe Berrios lost his reelection bid.

She is running unopposed in the Nov. 6 general election.

Other candidates in the race have already started to take shots at Preckwinkle. Troy LaRaviere, president of the Chicago Principals and Administrators Association, said her “failure to stand up to Emanuel” in the 2015 election “tells me that she would fail to stand up to the banks, real estate developers, and school privatizers who used Emanuel to rob and exploit Chicago residents.”

Activist Ja’Mal Green planned to hand out “Queen Sugar” shirts — a reference to the failed sweetened beverage tax that Preckwinkle championed. Green said “she has worked tirelessly amongst the establishment and has failed to create innovative ideas to put Chicago ahead of other cities. Her tax now, fix later approach has put a strain on Chicago residents for years.”

Preckwinkle also faced questions over the resignation of her chief of staff, John Keller. Keller resigned earlier this week after allegations of “inappropriate and disrespectful behavior.”

A brief statement Preckwinkle’s office sent out Tuesday night was intended to protect the privacy of the woman involved in the situation, a spokesperson for Preckwinkle said, but when more questions came in and the situation snowballed, Preckwinkle’s office sent out a second, more detailed statement on Wednesday — forcing the board president to do damage control the day before her mayoral announcement.

In a letter to employees in offices under the president that went out Thursday, Preckwinkle said as president and “as a woman, it is important to me to foster a workplace that is respectful, where all people are treated with dignity.”

In a brief press conference after her mayoral announcement, Preckwinkle said she couldn’t say much about the situation because she doesn’t want the woman involved “to be victimized a second time.”

She added: “What’s important here is I have zero tolerance towards harassment of any kind. I learned about this allegation on Friday, after corroborating it on Tuesday I demanded his resignation. I believe we need to treat each other with dignity and respect at all times.”