CHICAGO (CBS) —  It was one of the worst kept secrets: Illinois State Comptroller Susana Mendoza is now running for mayor of Chicago.

And that sets up an extraordinary campaign showdown against another highly accomplished woman: Cook County Board President Toni Preckwinkle.

It’s not exactly a surprise since an announcement video leaked out before Mendoza won re-election as state comptroller.

“I think that Chicago does not need a caretaker mayor or someone who’s part of the status quo,” said the 46-year-old Mendoza.

That’s a clear shot across the bow of 71-year-old Toni Preckwinkle who wouldn’t directly criticize Mendoza.

“Anyone is entitled to run for mayor,” Preckwinkle said. But her supporters weren’t holding back.

“Susana Mendoza is Rahm’s third term, there’s no doubt about it,” said 48th ward alderman Carlos Ramirez-Rosa. “She was an attack dog for Rahm during his 2015 reelection effort attacking progressives, making sure we didn’t have that change in City Hall.”

“Nobody tells me how to do the job or what to do,” said Mendoza. “And I certainly don’t take any direction or orders from the mayor or anyone else.”

Preckwinkle insisted her long-standing progressive credentials set her apart.

“I was one of the three founders of the Progressive Caucus in the City Council,” said Preckwinkle. “In my 19 years there, I was sponsor of every single affordable housing ordinance that came before that body, every single living wage ordinance.”

And just as Preckwinkle will make special efforts to reach women voters, so will Mendoza.

“I want to see more women in elected office, in higher positions of authority, in leadership positions,” Mendoza said. “Because when women are in change, we govern in a different way than men do and that’s an exciting prospect,” said Mendoza.

Both Preckwinkle and Mendoza are expected to have well-funded campaigns. Preckwinkle already has support from two big public employee unions: the Chicago Teachers Union and the SEIU.

And Mendoza is expected to draw backing from trade unions close to Illinois House Speaker Mike Madigan and Chicago Mayor Rahm Emanuel.