Asked in an interview with Britain's Guardian newspaper why U.S. polls were split over the war in Iraq, the former Democrat president said:
"I think the basic reason is that our country suffered, in 9/11, a terrible and shocking attack ... and George Bush has been adroit at exploiting that attack and he has elevated himself, in the consciousness of many Americans, to a heroic commander-in-chief, fighting a global threat against America."
"He's repeatedly played that card, and to some degree quite successfully. I think that success has dissipated," he added.
"I don't know if it's dissipating fast enough to affect the election."
The Nobel Peace Prize winner described the invasion of Iraq by U.S.-led forces as "unwarranted" and "a completely unjust adventure based on misleading statements."
Carter also accused Bush of neglecting the nuclear non-proliferation work carried out by his predecessors.
"All of those long, tedious negotiations that were done by Dwight Eisenhower, John Kennedy, (Richard) Nixon and me and (Ronald) Reagan to control the spread of nuclear weapons have been abandoned by Bush," he said.