EditorialKaren Lewis, President of the Chicago Teachers Union at a forum in Chicago on Sept. 13, 2011. Lewis, a formidable teachers union leader in Chicago who battled Rahm Emanuel when he was mayor, and who in 2012 led the city’s public-school teachers in their first strike in a quarter-century, died on Monday, Feb. 8, 2021. She was 67. Her death was announced by the Chicago Teachers Union, which did not say where she died. She had been under treatment for glioblastoma, an aggressive type of brain cancer that forced her to retire as head of the union in June 2018 after undergoing brain surgery. (Peter Hoffman/The New York Times)