One television advertisement by the Clinton campaign and another by a pro-Clinton Super PAC employ apocalyptic images of mushroom clouds to warn that Trump can’t be trusted with the awesome power of nuclear weapons. But in an interview with Reuters this week, Trump charged that it is Clinton, with her talk of intervening in Syria, who would start “World War III” with nuclear-armed Russia.

Each campaign feels it has the upper hand in the politics of Armageddon, which experts call a newly tangible threat amid surging tensions between the U.S. and Moscow.

Nuclear policy experts consider the talk of nuclear war — which has come as a surprise to them — a mixed blessing, potentially educating the public about nuclear issues but also frightening people at home and abroad to a degree unseen since the mid-1980s.

“There is a fear in the American public that you haven’t seen for a long time,” said Joe Cirincione, president of Ploughshares Fund, a nonprofit that promotes global denuclearization. “There’s also a global fear,” Cirincione added, noting that on Thursday the United Nations General Assembly voted 123-38 to begin negotiations toward a treaty banning all nuclear weapons.