They get together around openings and, well, closings. That is to say, current and former presidents seem to gather only for the openings of presidential libraries and funerals.
President Obama and the four living former presidents gathered today at the dedication of the George W. Bush Presidential Library and Museum on the campus on Southern Methodist University. They showed up, I presume, as a sign of respect for the office and for their extraordinary shared experiences, and, perhaps, as a nod to their shared concerns about legacy.
"When you've had the honor of being president and your ambition is slaked, and most of your fights are done," said President Clinton in 2011, "all you really want to do is make sure that by the time you leave this earth, things are a little better off than they were when you showed up."
And so the five men who are or have been President have gone out of their way to showcase their bedrock commitment to one common belief: Volunteers are part of the answer, and service is part of who we are as Americans.
President Carter began working with Habitat for Humanity after seeing an older woman living in a tenement in New York City. "There was no water, no heat, no electricity," he said. "She was cooking her meal on a trash fire that she built between two bricks. I realized how much Habitat could mean to a neighborhood like this." For almost 30 years now, Jimmy and Rosalynn Carter have given a week each year to build homes for those who need them.
President George H.W. Bush's legacy will likely be built on volunteer service. In his acceptance speech at the 1988 Republican National Convention, Bush spoke of America's volunteer organizations as "a brilliant diversity spread like stars, like a thousand points of light in a broad and peaceful sky." Bush then went on to found Points of Light, a nonprofit that is now the largest organization in the world dedicated to volunteer service.
As he left office, the only thing Bush asked incoming President Clinton to do was to continue support for Points of Light. "It was a remarkable thing that he would ask Bill Clinton for anything," says Jim McGrath, who handles media relations for the Bushes. "He's not one to ask anyone for favors or to burden anyone."
As it turned out, it wasn't the only thing George H.W. Bush asked of Bill Clinton. The two became an unlikely - and powerful - duo, pairing up to raise millions for hurricane and tsunami relief.
President Obama saluted Bush - and service - just a few weeks ago when he allocated $10 million in his budget for the Volunteer Generation Fund, which he named after George H.W. Bush. The fund will provide competitive grants to support the recruitment, management and training of volunteers in direct response to critical national problems.
While in office, President Clinton founded AmeriCorps, which has for 20 years now engaged hundreds of thousands of people in full-time national service. And since he's left office, Clinton's Global Initiative has marshaled the volunteer efforts of thousands to improve the lives of millions worldwide.
President George W. Bush continued this robust support for service, growing the Peace Corps to its highest level ever and AmeriCorps by 50 percent in addition to creating the Citizen Corps. So far, he is enjoying a much quieter post-presidency, but next month he'll host his third annual 100-kilometer, three-day mountain bike ride with wounded war veterans at his ranch near Crawford, Texas. And volunteer service is one of the featured values of his new Presidential Institute.
It's too soon to say what kind of volunteer service President Obama will incorporate in his life beyond 2016, but it seems clear that he'll follow the tradition of his predecessors: He'll volunteer and he'll champion volunteer service. It's what former presidents do best.
As Bush Sr. said in his inaugural address in 1989, "The old ideas are new again because they are not old, they are timeless: duty, sacrifice, commitment, and a patriotism that finds its expression in taking part and pitching in."
Our presidents have been the most powerful men on earth, but it is in the humble act of serving others that they demonstrate America's greatest strength.
Follow Michelle Nunn on Twitter: www.twitter.com/@pointsoflight