The following comes from a February 19 Washington Post article by David Weakliem:

It’s clear that Congress has become more polarized in the last few decades — there are more conservatives and more liberals, and fewer moderates — but has the general public become more polarized? That’s a more difficult question, but we can use the General Social Survey, a large national survey that began in 1972 and has been conducted every year or two since then, to try to answer it.

And attitudes toward abortion are one critical measure of polarization.

The General Social Survey regularly asks “whether or not it should be possible for a pregnant woman to obtain a legal abortion” in a number of different circumstances.

For one thing, fewer people support abortion in what are generally considered the most extreme or extenuating circumstances. Support for abortion if there is a chance of serious defect has fallen from about 85 percent in the 1970s to about 75 percent today. So has support for abortion if the pregnancy was a result of rape. Until the 1990s, more than 90 percent of Americans supported legal abortion if a woman’s own health was seriously endangered; in the last 10 years, the average has been about 87 percent.

And yet at the same time, more people support legal abortion for any reason, no matter why a woman wants it. About 35 percent held that view in the 1970s — but the number has risen to 45 percent in 2014.

In short, over the past 40 years, public opinion about abortion has become more polarized. More people say it should be illegal under all or almost all circumstances; and more people say it should simply be legal without any conditions. The number of people who hold the middle view — that abortion should be allowed in some circumstances but not in others — is declining.