Presidential nominees are not supposed to talk about the intelligence briefings they receive as part of their race for the White House. The secret information is supposed to help them fully prepare for the presidency — not to be discussed publicly on the campaign trail.

Republican presidential nominee Donald Trump at a rally in Aston, Pennsylvania, September 22, 2016. REUTERS/Jonathan Ernst

Yet that has already happened. We’ll see if it happens again during the debates Monday night.

During the NBC Commander-in-Chief Forum earlier this month, Matt Lauer of the Today show asked Republican nominee Donald Trump whether anything in the briefings caused him “shock or alarm.”

“Yes, there was one thing that shocked me,” Trump replied, “and it just seems to me that what they said — President Obama, Hillary Clinton and [Secretary of State] John Kerry, who is another total disaster — did exactly the opposite."

Trump elaborated on the briefing sessions: “I have (sic) pretty good with the body language. And I could tell they [the briefers] were not happy. Our leaders did not follow what they were recommending.”

There were several immediate problems with Trump’s answer. First, on the most basic level, he did not explain what he meant by “body language.” Did the intelligence professionals squirm? Wiggle? Did they grimace or smirk? Raise an eyebrow?

Voters watching were left to wonder, as they do so often in this bizarre election year.

Most important, however, the briefers are intelligence analysts whose job does not include recommending anything. The analysts sift through information flowing in from a multitude of sources, including the CIA’s clandestine service that provides information from spies it recruits, electronic intercepts, overhead satellites and foreign radio broadcasts and publications. They synthesize and summarize all the information, and their analysis is then made available to government officials to assist in making policy.

Their task in a presidential election is much the same. They are to bring the nominees up to date on the major conflicts and issues around the world, based on information gathered by the CIA, the National Security Agency and the other U.S. intelligence agencies. The briefings so far have likely covered topics such as Islamic State, the civil war in Syria and the refugee crisis in Europe, Washington’s brittle relations with Moscow, North Korea’s nuclear tests, turmoil in Iraq and Afghanistan and terrorism.

Lauer was widely criticized for the job he did as moderator. But here he twice cautioned Trump to answer the question "without going into specifics." Trump, however, managed to assert that the administration and his opponent were not following what the briefers "were recommending" — even though the briefers would not be suggesting policies.

They might have described, for example, how fewer recruits are flowing into Syria from the West because Islamic State has lost control of a good deal of its territory. But as analysts, they would not have recommended that Washington increase its support for one faction or another.

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Former intelligence officials were appalled at what Trump said. "That's just awful," former CIA Director Michael Hayden told Politico. "A candidate used the intelligence professionals who were briefing him in an absolutely nonpolitical setting, he imputed to them views that were politically useful to him in the moment."

Hayden, a retired Air Force general who also served as head of the NSA, has not endorsed either candidate. But he has warned that Trump’s election would create havoc in the relationship between the military and its civilian leadership.

This isn’t the first time intelligence briefings have become entangled in election politics.

The tradition of providing classified information to presidential candidates began in 1944, when President Franklin D. Roosevelt made wartime intelligence reports available to the Republican candidate, Thomas E. Dewey. In 1952, President Harry S. Truman made CIA information available to Republican nominee General Dwight D. Eisenhower and Democratic nominee Adlai Stevenson.

In 1960, however, politics entered the presidential nominees’ intelligence briefings. The results proved highly unfortunate for the nation.

In that election, the GOP nominee, Vice President Richard M. Nixon, announced his opposition to a covert plan that he had actually helped devise. Meanwhile, his Democratic opponent, Senator John F. Kennedy, managed to both support the plan and then oppose it.

CIA Director Allen Dulles had flown to Hyannis, Massachusetts, to brief Kennedy. Shortly before the election, Kennedy put out a statement urging support for forces opposing Cuba’s new leader, Fidel Castro, both inside and outside the island nation, with the “hope of overthrowing” him.

Nixon was furious, he later confirmed in his book, Six Crises. As vice president, he had been an architect of the Eisenhower administration’s covert CIA plan to train Cuban exiles to do just that. Nixon believed Dulles told Kennedy about the plan, though Dulles later denied it.

The Kennedy camp knew that Cuban exiles were training in Florida, however. It was pretty much an open secret. Life magazine published pictures of the trainees a week before the election.

After Kennedy’s response, though, Nixon decided to publicly oppose the invasion that he had helped plan. “The covert operation had to be protected at all costs,” he wrote. “I must not even suggest by implication that the United States was rendering aid to rebel forces in and out of Cuba. In fact, I must go to the other extreme: I must attack the Kennedy proposal to provide such aid as wrong and irresponsible.”

The truth was that Nixon had actually been hoping the invasion of Cuba would take place before the election and help clinch his victory. But it didn’t happen. And Kennedy, who was advised during the campaign that favoring support for the rebels was a political mistake, reversed his position. He sent a telegram to Nixon. It said Kennedy had “never advocated and I do not now advocate intervention in Cuba.”

Kennedy won the election, and, in April 1961, he launched the Bay of Pigs invasion of Cuba. It failed disastrously. More than 100 Cuban exiles were killed, and almost 1,200 captured. Ten Cuban exile pilots and four U.S. pilots recruited by the CIA also died.

In a democratic system, the voters are supposed to listen to the candidates and make a choice. But in this instance, a major campaign issue — what to do about Cuba — became distorted. Voters were left with no true idea of where the candidates really stood. And also with no real public debate about the issue.

Many historians believe the failure of the Bay of Pigs invasion emboldened Soviet leader Nikita S. Khrushchev to send missiles to the Caribbean isle, leading to the 1962 Cuban missile crisis. Over those 13 days in October, the world faced a nuclear confrontation.

The lesson of the 1960 election is that it matters what the presidential nominees say during a campaign. One wonders, if Trump wins, how he might interpret the body language of Kim Jong Un, the volatile and unpredictable leader of North Korea, who claims to have an arsenal of nuclear missiles that the Pentagon warns might “be capable of reaching much of the continental United States” by 2020.

A mistake in reading Kim's body language — or Russian President Vladimir Putin's — could lead to unimaginable consequences.

Presidents had better rely on something more than body language in making decisions that could affect the millions of people around the globe.