Mayor Rahm Emanuel has been unusually silent on the matter of a possible sale of the Thompson Center, preferring not to get in the middle of the death match between Gov. Bruce Rauner and Illinois House Speaker Michael Madigan that is preventing a sale from moving forward. Until yesterday. The mayor said the city will block any attempt by the state to sell the Helmut Jahn-designed building until he has concrete assurances that Chicago taxpayers will not be left bearing the brunt of the costs of rebuilding the subway station underneath, according to DNAInfo Chicago.

Emanuel, speaking at an event promoting park and library improvements in Bronzeville, said, "I'm not going to stick that tab on Chicago taxpayers."

Rauner's complicated plan to sell the Thompson Center is contingent on several factors falling into place. One of the most important is securing Chicago City Council approval to change the zoning on the site to allow any potential buyer to build a new ground-up development or adaptive reuse to include a 115-story tower.

Emanuel's concerns echo those of Madigan who, in a letter to Rauner in March, said Rauner's plan to sell the building interferes with Chicago's zoning authority over the property. Emanuel estimates it would cost between $80M and $120M to rebuild the Clark/Lake station, where six of CTA's seven rail lines intersect and 5 million passengers pass through annually. State officials dispute that number. Rauner, who said a Thompson Center sale could command bids of up to $300M, said Emanuel is trying to "extort state taxpayers for more than what the property is worth."