Hillary Clinton gives two popes a shout-out in her new book—though one of them is by way of a quote that appears to be apocryphal.

In What Happened, her widely anticipated account of the 2016 campaign, Mrs. Clinton writes that a TED Talk given by Pope Francis earlier this year helped her move beyond anger following her unexpected loss to Donald Trump.

She writes about whether she can empathize with Mr. Trump’s supporters, many of whom told journalists and pollsters that fears about their economic situations drew them to Mr. Trump’s promise to revitalize the economy. She struggled to be empathetic because of the fears some minorities expressed to her about living in the United States following the election. She pointed to the numerous articles in national newspapers seeking to provide an understanding of the motivations of Trump voters, wondering why it was up to her and her supporters to open their hearts to people with opposing political views—and not the other way around.

“And yet I’ve come to believe that for me personally and for our country generally, we have no choice but to try,” she writes.

Then she writes about the pope’s TED Talk, which she describes as “amazing”:

He called for a “revolution of tenderness.” What a phrase! He said, “We all need each other, none of us is an island, an autonomous and independent ‘I,’ separated from the other, and we can only build the future by standing together, including everyone.”

She continues: “He said that tenderness ‘means to use our eyes to see the other, our ears to hear the other, to listen to the children, the poor, those who are afraid of the future.’” She said the pope’s talk is among the things she has thought about during long walks near her New York home.

“I’m coming around to the idea that what we need more than anything at this moment in America is what you might call ‘radical empathy,’” she writes.

Pope Francis dropped his surprise TED Talk in April. A papal first, the video urged individuals to work toward a future that lifts up society’s most marginalized, including migrants, the sick, the unemployed and prisoners.

Pope Francis makes a couple of other appearances in What Happened, which was released Tuesday and quickly became the best-selling book on Amazon. Mrs. Clinton recalls the back-and-forth between Mr. Trump and Pope Francis during the campaign, when the pair exchanged words over immigration. She also notes that the pope was the subject of one of the most shared pieces of fake news during the campaign, an article claiming he had endorsed Mr. Trump.

Mrs. Clinton’s book does not contain explicit references to many of the Catholic-related news stories from the campaign.

For example, she recounts how WikiLeaks hacked the email account of her campaign chairman, John Podesta. In some of the leaked emails, Mr. Podesta and some of his associates, all Catholic, write about trying to influence the church. In response, Archbishop Charles Chaput of Philadelphia wrote that the emails were “contemptuously anti-Catholic” and the then-president of the U.S. bishops conference, Archbishop Joseph Kurtz, wrote they were “troubling both for the well-being of faith communities and the good of our country.”

Mr. Trump highlighted these charges of anti-Catholicism during the Al Smith Dinner, a fundraising event hosted by Cardinal Timothy Dolan where both candidates appeared on stage together just weeks before the election. Mrs. Clinton did not write about this event in the book.

Regarding the email hack, Mrs. Clinton writes that Mr. Podesta “took it in stride. He felt bad about some of the language he used. He felt even worse for the friends and colleagues who had sent him private messages and now had to see their words printed for all to see.”

Initial exit polls showed that Mr. Trump won more Catholic votes than Mrs. Clinton, though a more detailed analysis conducted several months after the election suggested that Mrs. Clinton may have actually eked out just a few more.

Mrs. Clinton also takes up the subject of how the Democratic Party should approach abortion.

Mrs. Clinton also takes up the subject of how the Democratic Party should approach abortion. She reflects on an ongoing debate about whether the national Democratic Party should support national and local Democratic candidates who support restrictions on abortion..

She notes that she “picked as my running mate Tim Kaine, a Democrat personally opposed to abortion because of his Catholic faith but supportive of women’s rights as a matter of law and policy.”

She argues, however, that abortion rights must remain a priority of the party. “But when personal views on abortion become public actions—votes on legislation or judges or funding that erode women’s rights—that’s a different matter,” she writes. “We have to remain a big tent, but a big tent is only as strong as the poles that hold it up. Reproductive rights is central to women’s rights and women’s health, and it’s one of the most important tent poles we’ve got.”

In response to this section of the book, Kristen Day, head of Democrats for Life, tweeted, “Hillary’s comments make me happy I did not vote for her. Abortion extremism will kill the Dem Party.”

She writes about how during difficult times in her life, she turns to the words of a Dutch Catholic priest, Henri Nouwen

Mrs. Clinton writes about her own Methodist faith, a subject that was not discussed frequently on the campaign trail. Earlier this year, reports said Mrs. Clinton is considering how to become more involved in her church, including preaching.

Toward the beginning of the book, she writes about how during difficult times in her life, she turns to the words of a Dutch Catholic priest, Henri Nouwen, re-reading his book The Return of the Prodigal Son following her loss:

It’s up to us to make the choice to be grateful even when things aren’t going well. Nouwen calls that the “discipline of gratitude.” To me, it means not just being grateful for the good things, because that’s easy, but also to be grateful for the hard things too. To be grateful even for our flaws, because in the end, they make us stronger by giving us a chance to reach beyond our grasp…

My task was to be grateful for the humbling experience of losing the presidential election. Humility can be such a painful virtue. In the Bible, Saint Paul reminds us that we all see through a glass darkly because of our humbling limitations. That’s why faith—the assurance of things hoped for and the conviction of things unseen—requires a leap. It’s because of our limitations and imperfections that we must reach out beyond ourselves, to God and to one another.

In the same section where she quotes Father Nouwen, she writes about learning to be grateful again and “accepting invitations to events that spoke to my heart,” including a speech to Planned Parenthood—perhaps a demonstration of why even faith talk might not have helped Mrs. Clinton with some Catholic voters.

Each chapter of What Happened concludes with a short quote from a famous activist, politician or writer. One chapter, entitled “Making History,” ends with a quote from Catholic writer Flannery O’Connor: “To know oneself is, above all, to know what one lacks. It is to measure oneself against Truth, and not the other way around.”

The final chapter closes with a quote attributed to Pope John XXIII, who was made a saint by Pope Francis in 2014. “Concern yourself not with what you tried and failed in, but with what is still possible to do,” Mrs. Clinton writes. It is not readily clear where the quote comes from. While it appears on many inspirational-quote websites, it does not appear to be taken from official Vatican documents or writings of the saint.

Michael J. O’Loughlin is national correspondent at America and author of Hidden Mercy: AIDS, Catholics, and the Untold Stories of Compassion in the Face of Fear.