A recent public opinion survey found increasing support among Catholics for same-sex “marriage,” raising the question of whether the people behind the poll were trying to advance an agenda.

But Father Donald Paul Sullins doesn’t find the survey results that surprising. A professor of sociology at The Catholic University of America, Father Sullins said that such findings are reflected in the “General Social Survey,” which he calls “the gold standard for objective, unbiased social-science opinion research.”

A fellow with the Institute for Policy Research and Catholic Studies and a 2010 Ignatius Loyola Fellow at the Center for the Advancement of Catholic Higher Education, he is the author of numerous books and articles, including Catholic Social Thought: American Reflections on the Compendium, with Anthony Blasi, and “American Catholic and Same-Sex Marriage,” published in the Catholic Social Science Review.

He has conducted studies on a variety of subjects, including “Religion and the New Immigrants,” and his clients have included the Archdiocese of Washington, USA Today and the Pew Charitable Trusts.

Recent polls suggesting a shift in Catholic acceptance of homosexual unions, including same-sex “marriage,” have provoked considerable controversy, with headlines suggesting that the majority of the faithful have broken with their bishops. Some argue that the polling data have been intentionally skewed to support a “gay-rights agenda.” What has been the outcome of your research on this issue?

I analyzed the General Social Survey [GSS] to look at opinions on homosexuality and same-sex “marriage” (SSM) among American Catholics. I found that Catholics were more supportive of same-sex “marriage” — and more tolerant of homosexuality generally — than Protestants are. This is not a new or surprising development; it has been true ever since the questions have been asked.

I also found that tolerance of homosexuality has been growing since the 1980s among both Catholics and Protestants, and support for SSM has been growing since the 1990s. Tolerance and same-sex “marriage” support is also much higher among younger persons, both Protestant and Catholic. As these younger cohorts age into the mainstream of the population, it is likely that tolerance and support is going to increase.

The GSS asks whether the respondent thinks sexual relations between two adults of the same sex are “always wrong,” “almost always wrong,” “wrong only sometimes” or “not wrong at all.” I was interested in the number of Catholics who said “always wrong,” that is, they agreed with Catholic teaching. In the most recent surveys, 51% of American Catholics said homosexual relations were always wrong, but 69% of Protestants also said this. On SSM, the gap is even wider: 61% of Protestants oppose SSM, but only 39% of Catholics do. All these proportions have been dropping for the past 20 years.

So a majority of Catholics still think homosexuality is always wrong, but only two-fifths oppose homosexual “marriage.” How is this? The big change, and it’s true for both Protestants and Catholics, has been not among persons who oppose homosexuality — they still oppose SSM by and large — but among the growing minority who think homosexual relations are “not wrong at all.”

Do respondents distinguish between “tolerance” of homosexual unions and support for same-sex “marriage” or civil unions?

In the 1980s, most persons who thought that way made a distinction between tolerating homosexual relations as a private behavior and certifying it in a public status like marriage; that is much less the case today. Only 45% of those who think homosexuality is not wrong at all also supported SSM in the 1980s; today that figure is above 75%.

So the good news is that most Catholics still agree with the Church’s teaching on homosexuality; the bad news is that the level of agreement is dropping fast.

You note that “Catholic” states (those with a larger percentage of Catholics) have been more likely to support same-sex “marriage.” But the legislators, not the voters, have passed legal same-sex “marriage.”

Second, to what degree is this phenomenon the fallout from John F. Kennedy’s “solution” to conflict between the faith and political commitments of Catholic politicians? Might the record be different with different leadership?

What my research shows is only that voter opinion supporting SSM or civil unions is higher in states with a larger proportion of Catholics and lower in states with fewer Catholics (and more Protestants). One is welcome to counter that legislatures, or referenda, do not perfectly reflect voter opinion and are sometimes corrected by the voters in referenda; that is certainly true.

My point about referenda was only that no referendum has approved SSM, not only because the voters are always opposed to it, but also because in states where voters are likely to support it a referendum is not mounted. So in Vermont, for example, there was no referendum held on civil unions when the Legislature passed that law, because anyone considering mounting such a referendum would judge, correctly, that it would be very likely to fail in Vermont.

Certainly the record would be different with different leadership; the sad irony is that many legislators who support SSM claim to be faithful Catholics. But getting different leadership, in our system, depends directly on the will of the voters.

Should all “Catholic” respondents be lumped together in opinion research, as some studies do?

No. Active, church-attending Catholics are generally less accepting of homosexuality and SSM than are less active ones. But Catholics at every level of Church activity or commitment are more accepting of homosexuality than their Protestant counterparts.

What’s the connection between Catholics’ increasing tolerance of homosexual unions and political support for civil unions or same-sex “marriage”?

I found that the dropping opposition to homosexuality, especially among Catholics, is politically relevant. Voters still largely oppose SSM, but the level of opposition is declining. States with the highest proportion of Catholics in the population are the ones who have permitted SSM or civil unions.

Some advocates of traditional marriage have charged that many surveys signaling increased Catholic acceptance for same-sex “marriage” arise from agenda-driven opinion research. How should we assess the credibility of these studies?

The General Social Survey — what I used in my study — has been administered almost annually since 1972 by the National Opinion Research Center and funded by the National Science Foundation. It is the gold standard for objective, unbiased social-science opinion research and is the furthest you can get from agenda-driven data.

In today’s polarized political and media environment, just about any research announced with a press conference is likely to exhibit bias, and it’s certainly possible that PRRI has some agenda in publishing its study.

The proportions of support for homosexuality/SSM among Catholics they report are a little higher than those I found on the GSS, and some of their questions seem a little leading; but their basic findings and the trends they report are very consistent with what I found on the GSS, which is about as unbiased a dataset on public opinion as you can find.

If I have an agenda, it would be the opposite of that which PRRI is alleged to have. I am wholeheartedly supportive of the Church’s teachings in this area, and my study was published in the 2010 Catholic Social Science Review, the top journal for magisterially consonant social science research.

Yet my findings were very similar to those in the PRRI survey. One can look at rising Catholic tolerance of SSM and say further rise is inevitable. One can also look at rising Catholic tolerance of SSM and say the Church has a lot to do in this area. Either way, it is important to acknowledge the fact of rising Catholic tolerance of SSM.

Supporters of same-sex “marriage” point to shifting poll numbers signaling increased support for their goal. But every time the issue is addressed in a referendum, voters reject same-sex “marriage.” What’s the difference between an opinion poll and the election booth?

Support is increasing but has not yet reached majority in most settings. That will very likely change, and we will begin to see referenda that affirm SSM. Also, referendums are self-selecting to reject SSM to some extent. If there is enough support to have a referendum, there is more likely to be enough support to reject SSM-enabling legislation. States that now permit SSM have not had a referendum.

You say there has been a marked shift of Catholic opinion on same-sex “marriage,” as compared to Protestants.

Catholics have always been less opposed to SSM than Protestants, but the gap has recently widened dramatically. In the 1980s, Catholics were 8% below Protestants in the proportion opposed to SSM; today the difference has widened to 22%. Opposition to SSM has dropped among both Catholics and Protestants, but it has dropped much more among Catholics.

You suggest that young Catholics account for much of the difference between Protestants and Catholics on the issue of same-sex “marriage.”

The gap between Catholics and Protestants, with Catholics more supportive of SSM, is much larger among persons under 40. Younger Catholics are much more supportive of SSM, relative to younger Protestants, than are their respective elders.

You provide a number of reasons for Catholic tolerance of same-sex unions. Please discuss.

No one knows for sure why this is, but I offer some hunches. Catholics are more tolerant than other Americans on a wide range of moral issues, not just SSM. Catholics have a sense of minority status and a history of prejudice and being stigmatized in America, so it is natural that they would be sensitive to stigmatization and exclusion of other groups.

Also, Catholics in America experience a tension with public institutions that Protestants by and large do not. They also may feel less of a sense of ownership of American public institutions, like marriage, so they are less threatened by changes to civic institutions.

Tolerance of SSM is consistent with the history of recent American dissent from Church teaching on issues of private sexual morality that began with Humanae Vitae. On birth control, divorce and premarital sex, the American Church has tolerated widespread lay dissent, even among elite moral theologians and the priesthood; and this pattern, at least until recently, was also the case with SSM.

I think the bishops have also waffled on the issue a bit. When the bishops are hazy on the issue, it’s not surprising that the laity will be ambivalent. The American bishops today are much more clear on homosexuality and SSM than they were 20 years ago, which is a very promising development.

However, your research also notes that American Catholics are much less accepting of homosexual unions than their European counterparts.

We should acknowledge that both Catholics and Protestants in America are much less tolerant of homosexuality than is the case in most other industrialized countries.

Americans demand a higher level of public morality in their institutions, a kind of civil religion. This civil religion is fundamentally Protestant in form and sensibility, which may also contribute to the higher Protestant opposition protecting changes to the civil institution of marriage.

Has your research picked up on any recent changes in Catholic opinion, perhaps as a result of new initiatives by individual dioceses or the U.S. Conference of Catholic Bishops?

No, I used long-term national data, which are not sensitive to local or topical trends.

Why have polls become a predictable part of social movements and political campaigns? What do we want from polls? What do activists/politicians touting poll numbers want us to get from them? Are many of us conformists looking for direction?

First, we live in a political system where issues are decided and leaders are chosen by getting a majority vote. Politicians and activists use polls to get an indication on how well they’re doing and where they might have to work harder to succeed.

Second, each of us reads polls in order to locate our own opinions within the range of opinions expressed by others. We kind of locate ourselves within the community of opinion, and so know ourselves a little better, by learning how our opinion compares to those of other people.

The deeper question you may be asking is what relation poll results have to the truth of a matter. If a large majority of people think a certain way, does that create any greater presumption that that way of thinking is true? That, of course, depends to some extent on the type of truth or knowledge in question. But for spiritual or religious or scientific or metaphysical truth, the answer has to be No.

Register senior editor Joan Frawley Desmond writes from Chevy Chase, Maryland.