The Chicago Teachers Union currently finds itself in strange territory for a twenty-first century US labor union: defending a recent victory.

Labor has lost so often in recent decades that defeat has become most unions’ default position. So the CTU’s 2012 strike was a breath of fresh air for many American unionists: when unionized workers around the country were negotiating over the terms of their defeat, Chicago teachers fought back and actually won.

But such victories are never permanent. The contract the union negotiated during that strike has expired, and CTU members began voting Wednesday on whether to authorize another walkout. Assuming the union meets the legally required 75 percent threshold — quite likely given the strong internal push to vote “yes” — we will probably see another Chicago teachers strike sometime next year.