How a Think Tank Named the Range of Acceptable Politics

Joseph Overton worked at the Mackinac Center for Public Policy, a small libertarian think tank in Michigan. In the mid-1990s he was trying to explain to donors why some policy ideas could be openly debated and others got the messenger laughed out of the room. He drew a sliding window on a brochure. Inside the window: ideas a politician could endorse without losing reelection. Outside it: positions that read as radical or unthinkable. The window itself, he argued, was what shifted, not where any one politician stood.

Overton died in a plane crash in 2003. His colleague Joe Lehman named the concept after him and kept publishing it. The phrase escaped the think tank around 2010, picked up by political columnists trying to describe how same-sex marriage, marijuana legalization, and a federal minimum wage moved from fringe to mainstream over a decade.

The idea attracts fans across the political spectrum because it does not specify which direction is good. Activists on the right and the left use it to argue for staking out positions further from center, on the theory that pulling the window matters more than winning any single vote.

One thing the model does not measure is moral truth. The window tracks public legitimacy, which is a count of who can say a thing without consequences. That count moves for reasons that include argument, but also include media coverage, generational turnover, and which scandal landed last week. Overton drew a window, not a moral compass.