Learning about the Overton Window is one of those moments where a lot of things start to make sense.
Here's Wikipedia --
The Overton window is a political theory that describes as a narrow "window" the range of ideas the public will accept. On this theory, an idea's political viability depends mainly on whether it falls within that window rather than on politicians' individual preferences.[1] It is named for its originator, Joseph P. Overton (1960-2003),[2] a former vice president of the Mackinac Center for Public Policy.[3] At any given moment, the “window” includes a range of policies considered politically acceptable in the current climate of public opinion, which a politician can recommend without being considered too extreme to gain or keep public office.
Why does this concept matter?
Because suddenly you realize that a lot of radically advocated ideas aren't about actually getting their way, but instead about pushing the Overton Window out further.
Take a position that would seem basically insane -- let's say, giving a vote to every dolphin and chimpanzee worldwide, with animal caretakers voting for the animals -- and you'd scratch your head. It wouldn't seem to make sense.
But actually, if given a significant amount of press, that idea would make groups that care about the welfare of animals right now that seem "radical" start to seem more normal.
"Voting rights for monkeys? That's nuts. But yeah, they probably should be guaranteed higher quality of life in zoos, and minimum quality of life during farming should be much higher."
The Overton Window pushes two specific levers --
1. The natural human desire to compromise and take reasonable, moderate positions.
2. The fact that ideas that are too far outside of the mainstream get ostracized if suggested.
When more radical measures are suggested, it starts making previously radical ideas seem more reasonable. And then, rejecting a radical position often generates some desire to compromise by taking a lesser (perhaps previously seen as radical) position that seems moderate.
Most political parties do this -- at least, most effective ones do. Anyone not doing it would have their currently moderate position rapidly get re-cast as radical... so you get this strange back-and-forth, poor dialoging, ignoring reasonable points the other side makes, and people constantly trying to be shocking, etc.
It helps understand a lot of political dialog, especially when it's presented externally for the media and people who don't have a strong opinion on an issue currently.
Recommended as a jumping off point if you have free time and the topic interests you --
http://en.wikipedia.org/wiki/Overton_window