Marty Walsh grew up in a home with crosses in every room and big jugs of holy water from shrines all around the world. He was an altar boy and a favorite of the nuns at St. Margaret’s. They brought Mass cards to the hospital when he was 7 and very sick. His mother vowed she’d take him to Lourdes and Knock in Ireland in gratitude if he got well. He did. She took him. Then he grew up, ran for mayor of Boston, and won.

“Thy will be done” from the “Our Father” — Walsh repeated that as he went through the campaign. Before debates. During forums.  It was a suggestion from a close priest friend to give him strength. He also touched the rosary beads he carried in his suit pants pocket. He still does both.

Every night in their kitchen, his grandparents prayed the rosary. So when he was one of 35 American mayors chosen to meet Pope Francis in Rome July 22 to discuss climate change and human trafficking, it seemed only natural to show up with a gym bag holding dozens of rosaries and relics that friends and family sent from home. They wanted a papal blessing.

“When he walked into the room the whole place was kind of in awe. You could feel his presence and the spirit,” Walsh said this week remembering how he stood, with that gym bag, two feet from Francis. It was an experience he never, ever expected.

Right before that moment, “I pulled out my phone and went on the daily meditation from AA (Alcoholics Anonymous),” said Walsh, now going on 20 years sober. “It was the Saint Francis prayer. To me, there are no coincidences.”

Marty Walsh says his faith is strong and solid. It always has been. He prays every morning. He prays every night. He goes to Mass. He asks for guidance on political votes: the death penalty (against) and gay marriage (for). That’s how he voted when he was in the state legislature and those issues still divided Massachusetts. He asks for guidance now. Boston just gave up a chance to host the 2024 Olympics after Walsh refused to sign a document guaranteeing taxpayers would pay for cost overruns.

Does he have any doubts about his faith, that when he asks for such guidance, someone is listening?

“No,” he said, hesitating not even for a second.  “No, I don’t.”

You know, for those who struggle or waver in faith, it can be terribly reaffirming to find strong faith in a place you don’t necessarily expect it: the rough-and-tumble and often down-and-dirty world of politics. I don’t mean the evangelical politicians who bellow and brag about faith, using it as some sort of holier-than-thou campaign weapon. I mean the sort of politician in whom you see a certain unflappable resolve, a quiet assurance in decisions made. You see that and wonder where it comes from: Is this person a believer?

There’s no CATHOLIC stamped on Walsh’s forehead. But when you ask him, he tells you up front. Yes, he is a believer. He’s recites “The Serenity Prayer” daily, “living one day at a time, enjoying one moment at a time.” From childhood, he’s been steeped, just about marinated, actually, in Catholicism. He is the son of Irish immigrants out of Galway: Mary, a homemaker, and a John, a laborer. Close relations are priests and nuns. He grew up in Boston’s Dorchester neighborhood when almost everybody lived close in triple-deckers and parish defined your social life, your geography, and your world view. You may not make it to college. But very likely you’d get a good union job as a laborer, as Walsh did, or a cop or firefighter or electrician. You were well schooled not to ridicule the “down on their luck.” In other words, those struggling with addiction or the poor who might live next door.

“I think it comes from our upbringing, our roots,” said Raymond Flynn, who served as ambassador to the Vatican but also as another very Catholic Boston mayor. “My wife’s mother and father were born in the next village to Marty Walsh’s (parents). My grandfather was born in the next town over from Galway. I knew Marty’s father and his uncle was my labor leader. We’d see them all the time in church. That’s where we’d see people who worked all week long and now the one day they had off was Sunday and they’d pack up the kids and take them to Mass,” Flynn said. “That was part of who we were.”

Flynn remembered Richard Cardinal Cushing, once Boston’s archbishop, telling him a half-century ago, “Boston is a very proud city of rich immigrant Catholic faith.” Said Flynn, “That has always stayed with me.”

Marty Walsh said faith helped both him and his family get through the two major crises in his life. In grammar school, he was diagnosed with lymphoma, and doctors told his stunned parents he had but months to live. They didn’t even think he’d make it to First Communion in May. So they gave him a special Communion ceremony at Christmas. He received last rites twice. Yet the freckled little redhead did not die. After four years of intensive treatment and hospitalization, he recovered, cancer free, and became the neighborhood “miracle” child. His mother began planning their pilgrimages of thanks.

The second crisis: alcoholism. A bullet grazing his leg during a street fracas helped him admit, in his 20s, that he had a serious problem. “Back then I guess I was praying for the wrong reasons,” Walsh deadpanned about his faith life then. “I was praying to get me out of trouble. But when I got sober, my connection changed with God. I felt I was changed. I remember one of the first nights at a treatment center I asked for help and felt it was a different conversation I was having.”

Marty Walsh is 48 years old. He has never married or had children. But he and his long-time girlfriend just bought a house together, making him one of those “irregular” couples Pope Francis blessed at the Vatican. A socially liberal Democrat, he disagrees with many of the Church’s teachings. But he’s “asked for guidance” in reconciling his differences with Church positions. He says he is at peace with his conscience.

“The God I pray to,” says Walsh, “does not judge.”