Teachers are testing their political might in Chicago runoff

CHICAGO — The Chicago Teachers Union is one of the most powerful political institutions in this city. And it has more at stake in Tuesday’s mayoral runoff election than either man running for the office. Even in a Democratic stronghold awash with labor shops, the CTU has spent more than a decade cultivating a distinct and influential brand of street-fighting, social justice-driven unionism that addresses more than classroom size and teacher pay. Now the union is on the cusp of either elevating one of its own organizers into City Hall’s fifth floor office suites, or losing to a longtime foil…