Gloria Chapman can’t quite put her finger on what it is that keeps her marriage strong after 34 years of trials and separation.

Maybe it’s the sex — rare, but still electric enough to keep her giggling. Maybe it’s their faith, their professed love of Jesus Christ, that helps them endure the hardships.

Or maybe it was the murder, the cold, gutless assassination of a cultural icon that made her husband one of the biggest pariahs of the 20th century.

Mark David Chapman gunned down John Lennon outside the music legend’s Manhattan apartment just 18 months after Mark married Gloria.

And to hear her tell it, except for the distance and the time apart, they haven’t missed a beat.

“Our love has grown and grown,” Gloria says. “He tells me to remember love and intimacy comes first.”

In a lengthy interview with London’s Daily Mail, Gloria opens up about her relationship with Chapman, their conjugal visits and their galling advice to Paul McCartney and Yoko Ono.

But Gloria, 63, spends most of the time talking about her love ­affair with Chapman, a bond that has endured separation, distance, judgment and the abandonment of most of their friends.

Gloria still lives in Hawaii, where the Chapmans first met, and makes the 5,000-mile trip to see her husband in an upstate New York correctional facility.

There, the unlikely lovebirds get up to 44 hours alone, away from cameras and guards, to have sex, watch TV and share homemade pizza.

Chapman got the arrangement after he signed up for protective custody two years ago.

“It’s great,” Gloria says of the ­intimacy. “I go mostly for the family visits, because why go all that way and pay all that money otherwise. It’s a long trip and takes two or three planes to get there.

“I have 44 hours in a trailer home with him. It’s a single-wide. It has a little kitchen and a bathroom. If I was living there, I could probably go more often. It’s not at every prison but I have to bring all the food; they provide pots and pans.

“We make a homemade pizza bar by cutting the crust into four and we lay out all the cut-up peppers, tomatoes, onions, cheeses. We used to have salami.

“He gets two pieces and I get two pieces of whatever we want. Mark likes crunchy snacks — but no sweets — like chips, rice crackers and other good stuff. There is a TV and we’ll watch ‘Wheel of Fortune.’ ”

Eventually, the conversation drifts toward Lennon. It’s not a forced, elephant-in-the-room kind of talk, but a matter-of-fact conversation, like one about remodeling the kitchen or where to spend the holidays.

“Mark and I can talk about anything,” Gloria says. “We spoke about John on my last visit [in September]. We prayed for Yoko Ono. I’m a wife to Mark and I can identify myself with her more than anybody. I feel for her.

“One thing we prayed for is that she finds Jesus Christ in her life and to find forgiveness for Mark. She seems to be sympathetic towards him and I appreciate that very much. I hope someday I could meet her and express that.

“Mark and I both wrote her letters through her attorney. Mark isn’t angry or upset at Yoko [for fighting his parole]. I’m not sure exactly how he feels, but I’m sure he understands.”

Gloria says Chapman actually had a lot of affection for Lennon.

“He always says John is a kind and gracious person for taking time to talk to him and sign his ­album. John was a nice person but Mark wasn’t thinking about things and put himself first.

“Mark would say: ‘I’m sorry to cause such pain. I hope you forgive me. I don’t know how people can go through such hard things.’

“I’ve not gone through anything very hard. If I didn’t have Jesus in my life [when Mark murdered John], I’d have probably done something to myself or gone crazy. I’m very well, I work and keep busy. I love life.”

Gloria insists the murder brought them closer.

“I would say so,” Gloria says, nodding. “There were times when I couldn’t see him for three years because he didn’t want me to come to visit.”

Chapman met Gloria in March 1978. She was 26 and working as a travel agent while Chapman, 22, found work at a medical center in Kailua, Oahu.

A year later they were married.

By then, Chapman was already a religious zealot who, though a former Beatles fan, had turned against Lennon for once bragging that the Beatles were “more popular than Jesus.”

At his evangelical group, Mark sang the words: “Imagine there’s no John Lennon,” to the tune of Lennon’s hit song “Imagine.”

If nothing else, Chapman was honest, Gloria says. He told her of his plans to end Lennon’s life. She just didn’t take him seriously.

“I didn’t know what to do,” Gloria says now. “He totally convinced me that he got rid of the gun the second time.

“I was totally deceived, so I don’t feel guilty. I can’t live those kinds of regrets. I have to go forward or it could make me sick.”

Chapman blamed her anyway.

“It’s crazy,” Chapman once said. “I laid out the gun and I laid out all five bullets. She’d never seen a gun before. And I said this is what I was going to do.

“My God, I still have deep-seated resentment that she didn’t go to somebody, even the police, and say, ‘Look, my husband’s bought a gun and he says he’s ­going to kill John Lennon.’ ”

They managed to get past the finger-pointing.

“We have disagreements like regular people,” Gloria says.

She says she has even gotten past the abandonment of friends who didn’t understand why she stayed with Chapman. “Disappointingly, my close friends didn’t come around; they didn’t know how to react,” she says.

“Mark had close friends in high school and it took him a while to forgive them for not being supportive. I understand that people didn’t know what to do or say. My family has always been loving.

They kind of said, ‘Too bad.’ They are very supportive of me.”

But the answer to why she has stayed by Chapman’s side all these years is simple, Gloria says.

“My friends told me to get a divorce or annul the marriage,” she admits. “I was in turmoil because I still loved him and I had my whole life ahead of me.

“I read in the Bible in Malachi Chapter 2, Verse 16. I felt like it was God’s answer to me. It says, ‘I hate divorce.’ And that made my decision for me.

“That’s my answer, and divorce wasn’t an issue. I still loved him. And he would say, ‘Oh, just divorce me. Forget about me and get on with your life,’ but 35 years later, we love each other more than ever.”