The man who named the Overton window never got to see it used
The idea explaining why some political positions feel thinkable and others don't wasn't coined by its own author.
Joseph Overton was an electrical engineer turned policy analyst at a Michigan think tank in the 1990s, and he had a simple, almost boring observation: on any political question, only a narrow band of positions is considered respectable enough for an elected official to hold at a given moment. Positions outside that band aren't refuted so much as ignored, mocked, or treated as career-ending.
Overton drew this as a vertical range, from more government intervention to less, specifically to dodge the usual left-right framing. He died in a small-plane crash in 2003 without ever publishing the concept himself. It was his colleague Joseph Lehman who built it into a presentation, named it after his late friend, and spent the following years explaining it to other think tanks eager to learn how to move the range rather than just argue points within it.
The part people misuse most: the window doesn't move because someone wins a debate. It moves because enough people say the once-unthinkable thing out loud, repeatedly, without apparent cost, which is a much quieter kind of persuasion than anyone likes to admit.