Newlyweds Ian Alberg and Mary Morrison walk down the aisle after being married November 5, 2011 in a ceremony at the Sixth & I Historic Synagogue in Washington D.C. (Barbara Kinney/BARBARA KINNEY)

After Mary Morrison and Ian Alberg were declared married, Bill Clinton was the first person to stand and applaud. It was, after all, his presidency that brought the couple together.

For much of the 1990s they were among the young staffers keeping the West Wing in motion. Alberg first did advance work for the campaign and later became a domestic policy adviser for Al Gore; Morrison rose from intern to deputy director of Oval Office operations.

Morrison, Alberg and other White House employees in their 20s worked incessantly, and when they did take time to relax, it was often with each other. “It was like a fraternity and sorority,” Morrison says. “We literally did everything together.”

No one else seemed to understand the world they were living in, and outsiders constantly asked about Monica Lewinsky. “The last thing you wanted to do was go out with someone else who’d be like, ‘Is it true? Is it true?’ ” Morrison says.

When the administration ended in 2001, the group splintered. Some staffers, including Morrison, moved to New York to work at Clinton’s new office in Harlem. Alberg and others stayed in Washington.

Morrison returned monthly to visit her family in Arlington. On each trip, she’d schedule time with Alberg, just to catch up over brunch or dinner. Alberg did the same when he went home to see his family in Long Island, taking the train into the city to go out with Morrison.

“It was just so easy to be with her,” Alberg says. “There wasn’t any stress. And we were best friends. I don’t think either of us were thinking about it [romantically].”

In 2004, Alberg’s mother had a stroke and his visits increased. For six months, it seemed she was on the mend. But after a second stroke, she passed away.

“I relied on Mary emotionally for just about everything. I honestly don’t think I could’ve gotten through that time if it hadn’t been for her,” Alberg says. “That’s when I started to realize, ‘Hey, this should be something more.’ ”

Alberg had put his career on hold to care for his mom, and he saw less of Morrison in 2005 as he focused on his job at a law firm and rebuilt his life in Washington. By 2006, they resumed their twice-monthly visits. Both continued to date other people, but by the next year Morrison realized she had feelings for Alberg. “I always wished he was around,” she says.

She worried about telling Alberg. “It was that stupid cliche,” she says. “We really didn’t want to ruin our friendship.”

But in 2008, she grabbed his hand. Soon they were holding hands everywhere they went and occasionally trading chaste kisses, although it rarely went any further. “Then we were like, ‘Okay, what are we doing?’ ” she says.

“So we started to have the talk,” continues Alberg, now 42. “I thought, well, this is either going to work or we’re never going to be friends again.”

They knew so much about each other and had shared so much history that casual dating was not an option. “We knew if we started dating, we’d probably end up getting married,” Morrison says. “And I think we both probably struggled with [that].”

At Obama’s inaugural ball that January, friends saw them holding hands and asked what was happening, but the two still hadn’t defined the relationship. “In my mind, I was like, ‘Well, this is great. I kinda like it the way it is — we’re friends, we have benefits,’ ” Alberg says. “But it wasn’t a hookup, either. We were best friends.”

Later that year, as they sat on the steps of the Lincoln Memorial, they came to the conclusion that, practically speaking, they were already dating. It was just a matter of announcing it. They quickly did, and by the middle of 2009, their conversations turned to marriage.

Alberg says he never doubted the relationship but wasn’t sure he was ready for the next step. But by the next year, he decided it was time. “There isn’t anybody that I’ve ever felt this way about. There isn’t anybody I’m so comfortable with. There isn’t anybody else I can see spending the rest of my life with,” he says.

Morrison was expecting a proposal in Washington, so last Super Bowl weekend Alberg went to her home in New York. As she sat in sweatpants and glasses, he pulled out a ring. A week later, he took her to the Lincoln Memorial and proposed again, this time with her grandmother’s diamond.

“You’re never gonna find two people who had such a nontraditional love affair,” says Morrison, now 38, “but who really knew each other before they got married.”

On Nov. 5, the two wed at Sixth and I Synagogue in an interfaith ceremony conducted by an Episcopal priest and a rabbi. Morrison wiped tears from her eyes as they exchanged vows and read their ketubah, a Jewish marriage contract.

President Clinton beamed from the second row, next to his daughter, Chelsea, and her husband, Marc Mezvinsky. After the ceremony, the guests, including former congressman Anthony Weiner and his visibly pregnant wife, Huma Abedin, adjourned to a reception at the W Hotel.

“I did get to marry my best friend,” Alberg said after the wedding, “which is really cool.”