President Obama has picked Myrlie Evers-Williams, widow of slain civil rights icon Medgar Evers, to deliver the invocation at his public swearing-in later this month. It is believed to be the first time a woman, and a layperson rather than a clergy member, has been chosen to deliver what may be America’s most prominent public prayer.

The inaugural committee Tuesday plans to announce that the benediction will be given by conservative evangelical pastor Louie Giglio, founder of the student-focused Passion Conferences, which draw tens of thousands of people to events around the world.

The contrasting choice of speakers are typical of a president who has walked a sometimes complicated path when it comes to religion — working to be inclusive to the point that critics at times have questioned his faith.

In a statement released by the inaugural committee, the president said the careers of Evers-Williams and Giglio “reflect the ideals that the Vice President and I continue to pursue for all Americans - justice, equality and opportunity.”

Obama will privately take the oath of office for his second term on the constitutionally mandated date of Jan. 20, a Sunday. But the public ceremony will be the next day, coinciding with the Martin Luther King Jr. holiday. In a statement issued by the Presidential Inaugural Committee, Evers-Williams said “it is indeed an exhilarating experience to have the distinct honor of representing” the civil rights era at the Jan. 21 event.

This year is the 50th anniversary of the murder of Evers, who was the NAACP’s Mississippi field secretary at the time of his death. Myrlie Evers-Williams spent decades fighting to win a conviction of her late husband’s shooter, and served as chairman of the NAACP in the 1990s.

“I would imagine that even people who are made somewhat uncomfortable by the allusions to religion in such public moments will find an invocation by the widow of a martyr to be moving and poignant,” said author Jon Meacham, who has written on religion in American history. “This is as unifying a gesture as a president could make, it seems to me.”

The invocation comes at the start of the inaugural ceremony, and the benediction comes at the end. An inaugural official said Giglio was picked for the benediction in part because of his work raising awareness about modern-day slavery and human trafficking. Those were core issues at his most recent conference, Passion 2013, attended by more than 60,000 mostly young evangelicals in Atlanta.

“During these days it is essential for our nation to stand together as one,” Giglio said in a statement. “And, as always, it is the right time to humble ourselves before our Maker.”

Decades ago, few Americans paid attention to the clergy (always mainline Protestants) who stood on the podium with the incoming president, or the scripture upon which the president put his hand as he swore the oath of office. But as the country has become more politically polarized and religiously diverse, faith and politics have become far more explosive, and such official moments are now scrutinized.

Obama made news four years ago when he selected conservative megachurch pastor Rick Warren to deliver the invocation. The choice angered progressives who opposed Warren’s work to prevent same-sex marriage, but was seen by many experts as a sign of Obama’s willingness to work with religious conservatives after a bruising campaign.

With the country arguably even more polarized in 2013, historians of religion and politics said Monday that inaugural prayers can be a unifying balm in a nation that overwhelmingly describes itself as Christian. They said they expect Obama to include strong theological references in his address.

Shaun Casey, a Wesley Theogical Seminary professor who has written about faith and the U.S. presidency (and advised the Obama campaign on faith in 2008), said the president is like Franklin D. Roosevelt and Abraham Lincoln in that “he’s trying to unite the nation in the face of deep division and conflict. They are trying to coax more people into the national discussion . . . and this is the last time the entire nation will pay attention to what this guy says in one sitting.”

Some details of the inaugural ceremony have changed over time, including the move to the west side of the Capitol from the east side. But historians say the role of an unspecific deity has been a prominent constant. Lincoln’s address at his second inauguration is the most explicitly religious in history, Casey said.

It was only in the 1970s and 1980s, historians said, with the rise of the religious right and the culture wars that Americans started caring more about who was praying over the president on the podium and how.

“It became a way of making political statements,” said Randall Balmer, professor of American religious history at Dartmouth College.

Progressive evangelical leader Jim Wallis said he has been asked for guidance by some of the clergy who have been involved in previous inaugurations and also some involved this year. He said he warns them against “the temptation or danger” of being only a chaplain offering a blessing.

“When people ask my advice, I always say: ‘Use the occasion to remind our political leaders of their responsibility to the common good. Our involvement in these events should be prophetic in the biblical sense.’ ”

The inaugural committee would not release details about the scripture to be used for the swearing in. Presidents typically rest their hands on the Bible.

An interfaith National Prayer Service is scheduled Tuesday at Washington National Cathedral.