According to the latest Gallup polls, public opinion on issues of sexual and reproductive freedom has become steadily more liberal.
In 1977, Americans were evenly split on whether gay sex should be legal. Now they support its legality by a 2-to-1 margin.
In 1996, the country opposed same-sex marriage by 68 to 27 percent. Now it's a dead heat.
In 2002, a 50-to-45-percent plurality said it was morally wrong to have a baby outside of marriage. Now a 54-to-42-percent majority says it's acceptable.
Birth control, as an issue of private morality, is a nonissue: 89 percent of Americans say it's OK.
On issue after issue, the polls have moved to the left. But not on abortion.
In 1995, Gallup found that 56 percent of Americans identified themselves as pro-choice, while 33 percent identified themselves as pro-life. That gap closed within three years, zigzagged a bit, and by last year stood at 49 to 45 percent, a narrow pro-choice plurality.
In this month's poll, however, 50 percent of respondents call themselves pro-life. Only 41 percent call themselves pro-choice.
Advocates of abortion rights, responding to the Gallup report, point out that calling yourself pro-life doesn't mean you support every restriction.
The "vast majority of Americans continues to support legal abortion in all or certain circumstances," observes NARAL Pro-choice America, adding that "other independent polling shows little change."
NARAL cites data from the Pew Research Center showing that most Americans still think abortion should be legal in most cases.
Planned Parenthood offers the same rebuttal: "A majority of Americans still believe abortion should remain a safe and legal medical procedure for a woman to consider if and when she needs it, and these fundamental views have held steady for more than a decade."
But that's the puzzle. At best, support for abortion is barely holding its ground, way below support for contraception, while approval of gay sex and gay marriage are soaring.
Something about abortion continues to alienate people who are willing to take a more liberal view of birth control and homosexuality. What is it?
Pro-choice groups see abortion as an issue of women's rights, reproductive freedom and respecting privacy. But look at long-term data from the General Social Survey, a multidecade project of the National Opinion Research Center.
The survey shows that over the past 40 years, public opinion has shifted in the pro-choice direction on all three of those themes. And yet, contrary to the pro-choice inference, it hasn't shifted on abortion.
From 1972 to 2006, the percentage of survey respondents who said premarital sex was "not wrong at all" rose from 28 to 46. The percentage who said gay sex was "not wrong at all" tripled, from 11 to 32 percent.
And from the mid-1970s to the late 1990s - the years during which the survey asked about women's rights - opinions moved clearly to the left.