In one of her first takedowns of Donald Trump after securing the Democratic nomination, Hillary Clinton asked voters to consider whether they wanted erratic and unpredictable Trump with his finger on the nuclear button.

It turns out there is no button. But the process to make such a deadly, powerful decision is devoid of checks and balances and leaves the decision to launch nuclear weapons to the president alone with no opportunity for second chances, experts said.

People might assume such a critical call would have to be approved by a whole chain of command, but Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Center for Nonproliferation Studies, said the system is designed to work fast and have intercontinental ballistic missiles in the air within minutes of the president making a decision. As a result, while many people may be part of the process, they are there to carry out the president's order, not to question it.

"In movies, there's all this time and people argue and cajole. That is not how this system is designed," Lewis said. "It's designed so the president can say, do X, here's my authentication code."

Kingston Reif, director for disarmament and threat reduction policy at the Arms Control Association, said anyone in the chain of command could choose to defy the president, but that would be grounds for dismissal and essentially amount to mutiny.

"He has sole and absolute authority to order the launch of U.S. nuclear weapons, whether it be one or two or hundreds. Period. Full stop. It is his or her decision to make," Reif said.

While there is no button, there is a briefcase, called the "football." That briefcase, which is carried everywhere the president goes by a military aide, includes communication infrastructure and a very basic, small briefing booklet with a menu of inflexible war plans from which the president can pick, since these decisions are expected to be made within a minute or two, Lewis said. For example, the president may look at a series of war plans against a Russian attack and say, let's go with plan B, Lewis said. There are no opportunities to choose other targets or refine these pre-set plans.

The briefcase also holds a sealed packet with a tiny piece of paper, called a biscuit, that includes an authentication code. Lewis stressed that this code does not launch the nuclear weapons, but serves to let officials know that the order is actually coming from the president himself.

"It's 'I'll have a grande nuclear war,' rip open the packet, and give code," Lewis said.

Once the order is given and authenticated, the National Military Command Center formats it into an emergency action message, then sends it to the command center to actually launch the weapons.

The speed of this whole process does not allow for a president to change his or her mind once the decision is made.

"The system is designed to take the president's desire to retaliate and render that decision into an actual law in a matter of minutes. If a president actually sends the order, there is no time to countermand it. If he says 'Go,' then two minutes later says, 'I'm an idiot what am I doing?' the I'm-an-idiot message will never catch up," Lewis said.

Lewis also stressed that while the president has the sole authority to launch nuclear weapons, he or she does not have the ability to physically launch weapons. It may be the president's decision, but the people who actually launch the weapons are at a lower level in the chain of command.