A former Democratic senator of Georgia, Sam Nunn, has expressed interest in a presidential bid and is now one of 50 people who have discussed a bipartisan or independent presidential run with Unity08, a group founded by Democratic and Republican strategists who believe the two-party system is not helping to address the country’s most important problems.

Doug Bailey, a GOP political strategist and adviser to President Ford who is one of the group’s founders, said he and other officials of the group met recently with Mr. Nunn. Mr. Nunn, who is best known for his work on nuclear nonproliferation, served in the Senate between 1972 and 1996 and now runs an organization called the Nuclear Threat Initiative. He was out of the country Monday and could not be reached to comment, but he told the Atlanta Journal Constitution in an article published on Sunday that a presidential run “is a possibility, not a probability.”

“My own thinking is it may be a time for the country to say ‘Timeout.’ The two-party system has served us well, historically, but it’s not serving us now,” Mr. Nunn, 68, told the newspaper.

Mr. Nunn would be a surprising Unity08 candidate both because of his long-standing ties to the Democratic Party and the fact that stopping the spread of nuclear weapons, his signature issue, is already represented — or nearly represented — in the 2008 race by Fred Thompson. The former senator of Tennessee, “Law & Order” TV star, and all-but-certain GOP candidate even played the part of the president in a 2005 movie produced by Mr. Nunn’s nuclear institute called “Last Best Chance,” in which terrorists try to obtain materials for nuclear weapons.