If the vast majority of the electorate wants change, why is that change taking so long to materialize?

In fact, this kind of political paradox is not unusual. It has to do with the unique position abortion occupies in the realm of public opinion, according to the Temple University political-science professor Kevin Arceneaux.

One of the remarkable lessons about abortion gleaned from the United States, said Arceneaux, is that unlike other divisive social issues such as gay marriage (which Ireland legalized via referendum in May), “when you look at public-opinion polls there’s not been that much movement over time.” In the U.S., “if you ask people specifics about the circumstances under which abortion can happen you will see some differences. But if you just want to ask the question in general—‘Is this a moral thing?’—on that I think opinions have been pretty stable.” This has to do, he said, with the extent to which abortion is a visceral issue, involving a person’s intuition about what constitutes taking a life.

These gut feelings also mean that the wheeling and dealing politicians typically employ on other policy issues doesn’t work when it comes to abortion. Theoretically, Arceneaux observed, “you could have a party that had more people in it that were opposed to abortion but maybe they’re indifferent about it in some respects or there are other things they care way more about. The party could then logroll on that issue. They could say, ‘Well, the Labor Party really cares about abortion. Our voters don’t really care about abortion but they care about tax policy. We’ll give the Labor Party what they want on abortion and we’ll get what we want on tax policy.’”

But abortion isn’t tax policy. “The problem with abortion is that it’s a very difficult issue to logroll on. It’s difficult to compromise on,” Arceneaux said. Some policies with less public support than legalizing abortion may become law through ordinary political give-and-take, but abortion rights are not the type of thing to be legislated quietly. Which means that however much abortion might seem like a religious issue similar to gay marriage, the discourse about it winds up being more like the U.S. gun-control debate. “Organized interests play an outsized role,” because when you can’t do much to change minds, you need to mobilize the voters for whom this is the deciding factor in which candidate they vote for. In other words, you play to priorities.

“If you’re a politician, it would be suicide in many [U.S.] districts to support any gun-control legislation. You only need 10 to 15 percent of the district to say, ‘I’m going to vote for anybody else but you because of that,’” Arceneaux noted. Changing a public-opinion poll by 5 percent generally doesn’t matter much. Finding 5 percent of the electorate who will show up to the polls every time, and vote on a given issue every time, does.