CHICAGO – She’s brash and blunt, a union leader known for her tart tongue and flip one-liners often aimed at Mayor Rahm Emanuel in a bitter contract dispute regarded as a referendum on the future of Chicago schools.

But Karen Lewis – who recently referred to the high-stakes talks as “the silly part” of her day – also is a whip-smart Ivy League graduate with a long, distinguished record in the classroom and the overwhelming support of her union’s 30,000 members.

Two years after she took the helm of the Chicago Teachers Union, the former chemistry teacher finds herself at the center of a nationally watched confrontation with Emanuel, the equally tough and sharp-tongued former White House chief of staff.