"It's sort of a welcomed nuisance by each of these administrations," said Russell Riley, a presidential scholar at the University of Virginia Miller Center of Public Affairs. "President Carter's interventions have been useful but by the same token, if you're working in the White House and you're trying to choreograph a relationship with very difficult authoritarian regimes, having another independent actor in the mix can be as frustrating as it is helpful."
Carter is not the only former living president to be involved in international affairs. Clinton has been actively involved in world affairs, specifically relief efforts in Asia after the 2005 tsunami and in Haiti after the earthquake there last year. Former President George H.W. Bush has also been active in relief efforts in both countries, as has his son to a lesser extent.
But Carter doesn't enjoy the same kind of celebrity status as Clinton and observers say most of his work has been under the radar.
Carter, the least popular post-war president when ranked by job approval rating, has since then gained respect both on the global scale and domestically for his humanitarian work through the Carter Center. He's also faced his share of controversy, especially in advocating for Palestinians.
"This was a man who created enormous opportunities for himself after he left the White House as kind of a rejected political figure in 1980. And so in some respects what you see from President Clinton is, whether self-consciously or not, modeled after what President Carter has done," Riley said.