– When it comes to the Roman Catholic Church, Judy Donnelly has been something of a rebel over the years. Like much of Ireland, she supported contraception, voted in a referendum to legalize divorce and, three years ago, backed same-sex marriage.

That last vote was joyously celebrated around the country and the world, placing Ireland, which elected its first gay prime minister last year, at the vanguard of what many called a social revolution.

But when it comes to the historic decision on legalizing abortion, which will be put to the nation Friday, Donnelly says she will vote no, as will enough of her countrymen and women, including lawmakers across the political divide, to throw the referendum result into doubt. Polls for Friday's vote have narrowed so tightly in recent weeks that "yes" and "no" campaigners are not able to confidently predict a victory.

"It's just not the same," said Donnelly, 46. "It's about values and morals."

Even if Ireland is becoming more culturally liberal in many respects, opposition to abortion is deeply ingrained. To some, abortion amounts to murder rather than being about liberal cultural values.

Abortion rights advocates cite several reasons for why attitudes have not changed: a history of female oppression; the church's continuing grip over sexual education; and very private experiences around miscarriages, fetal deformities, adoption difficulties and spousal disagreements over whether to keep a baby.

At the same time, many Irish say, sex and sexual health remain somewhat taboo subjects. Often, the negative consequences of sexual activity, including infections or unplanned pregnancies, are seen through a moral lens rather than as health issues.

The Catholic Church opposes abortion, and some priests told their congregations that they would not be able to receive Communion if they voted yes.

Ironically, it was a gay prime minister, Leo Varadkar, who called for this referendum that will essentially ask voters to repeal a 1983 amendment to the constitution that gives a fetus the same right to life as the mother and allow unrestricted terminations of pregnancies for up to 12 weeks.

"I know I come across as a hypocrite," said Darren Haddock, 48, a cabdriver who initially planned to vote in favor of abortion because he saw it as a woman's right. But now, he said, "We're talking about hurting a life."

The referendum on same-sex marriage was different, he said. "The time was right for Ireland to come out of the Dark Ages, to break the shackles from the church, and it was a victory for people to stand up to it," he said.

Donnelly voted in favor of same-sex marriage because her sister-in-law was part of the first gay couple to get married in England. Another cousin is gay and recently got married, too.

When it came to abortion, she reflected on some of her other relatives who had had miscarriages. "And then you have people who cross over to England to get an abortion," she said, although she said there were some exceptions, as in the cases of rape or incest. "But just because you made a boo-boo doesn't mean you get an abortion."