“To be the mayor of this city, you need to have courage, you need to have strength and you need to be able to bring people together,” the former Police Board president and onetime federal prosecutor said at a hastily arranged news conference. “Many of us have been out here for months, making our case to Chicagoans. Anyone who decides to jump in to take advantage of today’s political news, I think a fair question to ask them is ‘Where have they been?’ ”