When discussing political polarization, there is an important concept called the Overton Window. The idea is that there is a range of political ideas that people will accept; anything outside of that is either radical or unthinkable.
This window's size and position can change: it may be unthinkable, for example, to kill the capital class and all intellectuals who oppose the inevitable historical wave that is Communism, until enough agitators or influencers have made the case that it becomes mainstream. Such a process can also be considered for--as an example--white supremacy in the United States.
It is an important concept as presumably most people would want certain ideas--such as killing the capital class or systematically oppressing minorities--to remain within the realm of "unacceptable." In the recent years of increasing political polarization in the United States, discussion about the Overton Window has come more into vogue.
However a few times--from both sides of the political spectrum--I have heard a few discussions that go something like this:
"Such-and-such group or idea is too radical / unthinkable."
"But the other side has lots of radical / unthinkable ideas, and by allowing or promoting my own side's radical / unthinkable ideas, we can shift the Overton Window."
I've heard this line of argument used to attempt to deflect criticism of groups such as Breitbart (and associates such as Milo Yiannopoulos) as well as Antifa and other advocates of "punch Nazis."
This line of reasoning is critically and importantly flawed. It assumes that the Overton Window has a fixed size, and if it were to expand in one direction, it must necessarily shrink in another.
However, this is both theoretically and empirically not true.
First, theoretically: the Mackinac Center (where the idea originated) makes it clear that both the size and the position of the Overton window can change--not just the position. If you push it in one direction, there's no reason to think that you are necessarily causing it to shrink from another.
Second, we can look to history. There are many cases in which the Overton Window shifted just one direction with relation to policy: that is, the position changed but the size did not (or did not much). You can think of many of these on your own, but one is with respect to Women's Rights. Various feminist movements in the west, over the last century-and-a-bit, have made it unthinkable to (for example) prevent women from voting, and have made it increasingly sensible or popular to believe that government should be involved with making sure women make the same amount of money as men in the workplace. A similar shifting occurred away from absolutist rule and feudalism (once acceptable and now unthinkable) and towards republicamism and democracy (once unthinkable and now policy).
However, in times of great political extremism, we see the Overton Window expanding dramatically. The best example we've discussed before is that of Germany in the late Weimar Republic, in our podcast episode, "The Effectiveness of Political Violence in History." In the late Weimar Republic, both Nazism and Communism became increasingly acceptable, and even popular. In 1919, the far-right German party received 10.3% of the vote, and the pre-Communist party received 7.6%, totaling about 18%. By 1930, the full-blown Nazis received 18.25%, and the Communists 13.1%, totaling 31.3%. By 1932 and 1933, they received together over 50% of the vote. Street chaos between these groups and a desire for a strong hand to get things under control led to even more radical thinking.
In this case, the Overton Window shifted far outward. Ideas such as exterminating Jews and exterminating the capital class were now acceptable and even popular. The Nazis won out, but Germany had not simply shifted right--it had become much more radicalized.
Next time you're considering how to handle political dialogue based on the Overton Window, just remember: it does not merely shift, it also grows.