The Overton Window is an important strategic concept for pro-life activists. It is a model for understanding how changes in political attitudes can change the policy options which the public can accept as legitimate.
Imagine a simple left/right access like the one below. There is a “window” of policies on that spectrum which are considered acceptable public policy options. A politician can take a position within this window without suffering electoral consequences.
According to this model of public policy, the job of pro-lifers is to pull the Overton Window in the pro-life direction. There are several major ways that this happens: 1) when a major event happens (for example when Planned Parenthood was revealed as selling human body parts, helping cover up statutory rape, etc), 2) by effective communication from education groups which change the worldview of the average citizen, and 3) by changing public policy and thereby opening up more policy options on our side of the spectrum.
That is why incremental pro-life policy battles are essential. Once it is seen as legitimate for pro-life groups to sometimes have their perspectives reflected in public policy, it becomes possible for us to be taken seriously on a larger range of issues. The more battles we win, the more legitimate our policy options become. In other words, every life we save through incremental laws makes it possible to save even more lives through effective political action.