Together, the two had weathered the near-death of their son in a 1989 car accident, Gore's vice-presidency, his loss of the presidency to Florida's notorious chad ballots, and then his reinvention as an environmental crusader.
But as their marriage passed the 40-year mark, their paths and expectations diverged, former Gore campaign manager Tony Coelho said.
"She went and did her thing," he said of Tipper Gore. "She was supportive, but she didn't share the world stage with him."
ABC News Analyst Cokie Roberts told "Good Morning America" today that the couple's announcement Tuesday caught her off guard.
"It's sad," she said. "These are nice people."
Roberts said she believes that the marriage's perserverance through the more difficult years gave the Gores a common goal that may have dissipated when life began to slow down.
"Is there another shoe to drop?" she asked. "Who knows."
Tipper Gore, once a very public figure herself, has increasingly kept out of public life, leading some to wonder if that difference caused a rift.
Though Al Gore's reinvention as a Nobel Peace Prize-winning environmentalist has led to many accolades, Roberts said, he eventually has to come home where "his wife knows he puts his pants on one leg at a time."
"It's much more fun to be a God than a person," she said.
Family therapist Terry Real told "Good Morning America" today that there may not be one smoking gun that ended the Gore's marriage.
He agreed with Roberts' assessment that the simple act of growing old together may have forced them apart.
"I think the moral of this story … is that nobody knows the inside of a marriage," he said. "People do grow apart."
"I think there have probably been fault lines in the marriage that have not shown in public," he said.
From Passionate Kiss to Divorce: 40-Year-Marriage Seemed Stable
For many, Al and Tipper Gore's relationship was summed up in a six-second kiss on stage at the 2000 Democratic Convention.
But over the course of the previous decade the couple went from loving "with my whole heart since the night of my high school senior prom," as Al Gore put it in 2000, to having "decided to separate," as they said in a statement Tuesday.
"We are announcing today that after a great deal of thought and discussion, we have decided to separate," the Gores said in an emailed statement. "This is very much a mutual and mutually supportive decision that we have made together following a process of long and careful consideration. We ask for respect for our privacy and that of our family, and we do not intend to comment further."
Sources, close to the couple, said infidelity was not the reason for the divorce.
Those looking for signs of strains on their relationship have to limit themselves to recent years. After their son Albert was injured in a car accident in 1989, the Gores entered couple's counseling and were virtually inseparable for the next 10 years.
In the early days of their relationship, "they were completely devoted to each other," said Robert Zelnick, a communications professor at Boston University and author of the biography "Gore: A Political Life."
"She had a tremendous amount of love for him. In the early days, they could not bear being apart. Witness his service in Vietnam, when she could barely come to grips with his absence," he said.
In 2002, during an interview with CNN's Larry King, Al Gore hinted at previous troubles the couple had and overcame.
"Well, we fell in love, and we've stayed in love, and we've worked very hard when there were hard times to work it out, and not that we ever thought about divorcing or anything like that. I don't mean to imply that. I mean that I think people need to work it out," he said.
The couple recently purchased an $8.8 million mansion in California, suggesting to some that they were seeking separate residences. Currently the couple live in Tennessee.
The couple met in high school, at a party after the senior prom, and they married at the National Cathedral in Washington on May 19, 1970. They have four adult children.