Amid protests over his positions on abortion and embryonic stem-cell research, President Obama spoke to graduates at the University of Notre Dame about coming together over disagreements by finding "common ground."
"Maybe we won't agree on abortion," Obama said during a speech interrupted by both hecklers and standing ovations, "but we can still agree that this heart-wrenching decision for any woman is not made casually. It has both moral and spiritual dimensions. So let's work together to reduce the number of women seeking abortions. Let's reduce unintended pregnancies. Let's make adoption more available. Let's provide care and support for women who do carry their child to term."
Other presidents have come to Notre Dame, and many had differences with the church -- as George W. Bush did on the death penalty and the Iraq war -- but none has faced the kind of organized uprising facing President Obama as he delivered a commencement speech and received an honorary law degree.
Obama responded with a call for "open hearts, open minds, fair-minded words," after entering an abortion battleground at the nation's pre-eminent Catholic university in South Bend, Ind.
"I do not suggest that the debate surrounding abortion can or should go away," Obama said. "Because no matter how much we may want to fudge it -- indeed, while we know that the views of most Americans on the subject are complex and even contradictory -- the fact is that at some level, the views of the two camps are irreconcilable."
Though Obama entered to applause, flashed a thumbs-up sign, and received standing ovations when receiving his honorary doctorate and delivering his speech, not everybody was happy.
In the emotional run-up to the speech, it didn't seem to matter to many conservative Catholics and anti-abortion groups what Obama said. To them, his support for abortion rights made him unqualified to be at the commencement ceremony.
"The concern is whether the University of Notre Dame, a Catholic university, upholds Catholic teachings or not -- and in this case, they are betraying the Catholic faith," said Patrick Reilly, president of the Cardinal Newman Society, an organization whose stated purpose is "renewing and strengthening Catholic identity" at the nation's 224 Catholic universities and colleges.
"President Obama is so sufficiently and strongly in opposition to the church teaching on these issues [such as abortion and embryonic stem-cell research] that it's completely inappropriate for Notre Dame to have him there," Reilly said.
In addition to a vocal hecklers who interrupted Obama's speech, protesters converged today on the university's front gates, and at least 27 people were arrested on tresspassing charges, police told the Associated Press.
Those arrested have included Norma McCorvey -- the "Roe" in the Roe v. Wade case that legalized abortion -- who now is an anti-abortion protester.
The anti-abortion movement had earlier called for the resignation of the university president, the Rev. John I. Jenkins, launched an online petition signed by more than 360,000 and lined the roads with posters of aborted fetuses -- a display that prompted at least one flash of anger from the general South Bend-area population.
"I shouldn't have to teach my 12-year-old what abortion is!" one woman yelled at a protester.
In a statement well before the ceremony, Jenkins wrote that the invitation "does not mean we support all of his positions … [on] abortion and embryonic stem cell research."
White House officials had said in advance that the president would address the protests in his speech, but wouldn't let it dominate his address. Today, they said, belonged to the graduates, more than 2,000 of whom are receiving their diplomas.
In fact, relatively few of the "Fighting Irish," as Notre Dame's sports teams and community members are known, have been among the protesters.
"Almost all of the opposition has been generated from groups outside the university," said the Rev. Richard McBrein, a Notre Dame theology professor.
Nationally, too, the Notre Dame hubbub appeared to be a debate the president is winning -- even among Catholics. One poll found 56 percent of all voters, and a whopping 60 percent of Catholic voters -- support Obama's appearance.
Even so, in addition to individual hecklers shouting interruptions during Obama's speech, some students bore silent protest.
"We are planning on putting a symbol on top of our mortarboards with a cross and a pair of baby feet," said one student, Stephen Govea, in advance of the speech.
Many did -- but others displayed symbols such as an "O" on their mortarboards in support of Obama.
A few students said they would boycott graduation.
"He may not see us on commencement day, but we are planning on praying," Andrew Chronister said. "And prayer can reach across space."
The most visible protests have been organized by outsiders like former presidential candidate Alan Keyes, who was arrested during a protest and then released, and Randall Terry, 50, the outspoken, sometimes in-your-face former head of Operation Rescue who was arrested a week ago and later sent his flock one by one into a polite police dragnet, where they were arrested for trespassing.
"Let's start filling the jails now," Terry said, "so we can have a witness that reaches to the world against this treachery and this betrayal."
Though the numbers of protesters leading up to the speech was relatively small, Terry predicted there would be hundreds more protestors during the Obama address -- and possibly hundreds more arrests.
Terry, the one-time Pentecostal lay missionary, spent much of the 1980s leading anti-abortion activists in large scale acts of civil disobedience -- including blocking entrances to family planning and medical facilities where abortions were performed. His protests garnered national media attention and frequently landed him in jail. In the years since he left Operation Rescue, he's run for public office twice -- and lost twice.
But now, he is back in the limelight, helping lead the six-week-old Notre Dame anti-abortion protest.
"Notre Dame is the premier institution of the Catholic church in the western hemisphere," Terry told ABC News. "Obama is the premier promoter of child killing in the western hemisphere. When you have that kind of epic thing going on, it demands a response from the whole Catholic world."
Terry converted to the Catholic faith a few years ago and has seized on the Obama commencement address at the famed Catholic university as a way of pushing the abortion issue back to the forefront of public consciousness.
"Abortion is an intrinsic evil. It is a higher crime than any other crime that we have on the face of the earth," Terry said in advance of Obama's speech, as his fellow protestors surrounded him outside of the main gate of Notre Dame, praying loudly.
"We want our bishops to start acting like apostles," he added. "If ... bishops really stood up and said, 'This isn't gonna happen,' we wouldn't be in this mess right now. The reason why we have President Obama is because our bishops do not rightly express their duty to defend life."
Despite the denunciations by protesters like Terry, Obama's effort to seek common ground with Catholics -- even though he supports abortion rights -- clearly resonates with many in the church.
"I wish Obama's views on abortion were different than they are," said the Rev. John Langan of Georgetown University. "But nothing convinces me that he isn't a morally sincere, sensitive person."
Still, conservative Catholics don't like him. And they're not shy about speaking their minds.
"You cannot say that I'm interested in social justice, and soup kitchens and the like, and health care, and at the same time be pro abortion," said Bill Donahue of the Catholic League. "He's got a real problem in the Catholic community."
Abortion isn't the only issue the conservatives object to. There's also Obama's support for embryonic stem cell research. And a liberal approach to gay rights.
"Never, in my 16 years of doing this job, have I ever seen the bishops collectively become as energized as they have been," Donahue said.
"There are even elements within the Catholic community that do not want to see his presidency to succeed," said Sister Jeannine Gramick of the National Coalition of American Nuns, shaking her head. "So, that's tragic."
But Catholics are not a monolithic voting bloc. Despite church teachings, Catholic voters have long supported abortion rights, stem cell research and the death penalty in the same proportions as all Americans. And 54 percent of them voted for Obama last November.
"The majority of Catholics are on Obama's side," Gramick said.
It may not have seemed so during the unrest at Notre Dame, but, "You don't always find out what a group is thinking by listening to the noisiest members," Langan said.
ABC News' Teresa Crawford and Karen Travers contributed to this report.