The Overton Window is a political theory that 'describes a "window" in the range of public reactions to ideas in public discourse, in a spectrum of all possible options on a particular issue.'
When I have heard the Overton Window discussed it is usually in reference to a later concept:
Other formulations of the process created after Overton's death add the concept of moving the window, such as deliberately promoting ideas even less acceptable than the previous "outer fringe" ideas, with the intention of making the current fringe ideas acceptable by comparison.
To summarise the idea in my own words: You can persuade people to move their opinion slightly and to accept ideas that are current unpalatable, by publicly proposing extreme, over-the-top views, until the more moderate versions seem like a reasonable compromise.
Wikipedia didn't cite any peer-reviewed articles.
Is there any research to support or discredit the idea that publicly proposing unrealistically extreme views tends to move public opinion toward more moderate versions that are in the same political direction?
(I learnt while researching this question, that there is a novel by political commentator, Glenn Beck, by the same name. I haven't read this novel, and I am not attempting to address any of its contents.)
Update: I see a few people repeating the claim in the comments, but still no-one has provided any evidence.
There is at least one competing model: that fringe elements on one side of a political spectrum will pollute the pool for others. That is, that people will dismiss moderate views because the extremists are so fringe. We could provide anecdotes for both of these theories, but that isn't evidence.