Polls show a wide majority of Americans support the Supreme Court’s decision in Roe v. Wade, which established a constitutional right to abortion. The Pew Research Center has repeatedly found that most Americans say abortion should be legal in all or most cases.

Yet even by the Pew measure, which has tended to represent the high-water mark for public support for abortion, only 59 percent of Southern Democratic leaners and 57 percent of Democratic leaners who attend church at least once a week say most abortions should be legal, according to Pew Research data from 2017.

When it comes to specific cases, things get more complicated. A recent Gallup poll found that 60 percent of Americans support abortion in the first three months of pregnancy. That number dropped to 45 percent — among the same respondents — simply by adding the condition “when the woman does not want the child for any reason.”

Gallup found majority support for legal abortion in the first trimester only in cases of rape or incest, when the woman’s life was in danger or when the child would be born with illness or disability. Similarly, the G.S.S. has found majority support for legal abortion only in cases of rape, when the health of the mother is at risk or when there is a risk of serious defect. The G.S.S. has never found majority support for legal abortion for, say, a low-income woman who can’t afford a child, or a married woman who doesn’t want more children.

What the G.S.S. has always found is that these issues don’t break neatly on partisan lines. They still don’t, although the parties today are more unified on abortion than they have ever been.

It is hard to reconcile it all. Many analysts or activists have tried, often in ways that show that their own views command majority support. But the most straightforward interpretation may be that the polls aren’t clear because for most Americans, abortion is a difficult, even wrenching issue that they can’t easily resolve for themselves, let alone the country.