"Do we want his finger anywhere near the button?" the Democratic presidential nominee asked a crowd in San Diego.
Her Republican opponent has vehemently rejected the attacks and said he would only use nuclear weapons as a last resort.
But in truth, there is no button. Instead, the president has a card, commonly called the "biscuit," with the nuclear launch codes on it. He also has a briefcase, nicknamed the "football," carried by a military aide, with the equipment and the information needed to launch a nuclear strike.
"You have to be ready anytime for any moment," said Pete Metzger, who for three years was one of the five alternating officers who carried the nuclear launch suitcase during Ronald Reagan's presidency. "Mind you, it has to happen quickly, because the time on a missile is very fast," saying it could take as little as five to six minutes for a nuclear warhead to hit Washington, D.C. or New York City.
The aide with the satchel is required to be close to the president at all times -- whether at the White House, in a motorcade, aboard Air Force One or on a trip overseas. The aide rides in the same elevator, stays on the same hotel floor, and is protected by the same Secret Service agents. There is also a football for the vice president in case the president is incapacitated.
The Presidential Emergency Satchel, as it is formally called, contains four things, according to former White House Military Office Director Bill Gulley's book "Breaking Cover."
There is a black book listing a menu of strike options; a list of secure bunkers where the president can be sheltered; instructions for using the Emergency Broadcast System; and a 3-by-5-inch card with authentication codes for the president to confirm his identity.
"It contains the equipment and the decision-making papers that the president would need to make a very quick decision" and to relay instructions to the National Military Command Center to launch a strike, according to Metzger.
Before being chosen as a military aide, Metzger said he underwent extensive vetting by the Defense Department, the Secret Service and the FBI, including psychiatric and psychological evaluations and "a very, very extensive background check."
The president, on the other hand, undergoes no such vetting, critics point out. And while the military officers who would carry out a nuclear launch are required to work in pairs, where both must concur before they can execute a nuclear launch, there is no such check on the president's actions.
"The president has supreme authority to decide whether to use America's nuclear weapons. Period. Full stop," said the Arms Control Association's Kingston Reif. A president could only be stopped by mutiny, he said, and more than one person would have to disobey the president's orders.
And as Reif points out, the stakes couldn't be higher: The size of America's nuclear arsenal gives the president "immense, unprecedented power. The US right now deploys approximately 900 nuclear warheads that are on the order of 10 to 20 times more powerful than the weapons that destroyed Hiroshima and Nagasaki. And those 900 warheads are available for use at virtually a moment's notice."
But Metzger said that, in his experience at least, the president takes the responsibility very seriously, as do the five military aides.
"The result of a decision the president would make is so grotesquely horrible -- it would change the face of the earth, it would change humanity, it would change mankind," he said. "I guess when you're on duty, you try not to think of the import of that. But you are fully prepared to do so if you have to."