What Donald Trump and Hillary Clinton Will Learn in Classified Briefings

Partisan concern over Donald Trump and Hillary Clinton handling classified information has created a public debate over whether they deserve to receive briefings from intelligence officials—a tradition that dates back more 60 years.

The process formally began for Clinton and Trump on Friday. But Clinton’s handling of classified information over email while she was Secretary of State was characterized as “extremely careless” by FBI Director James Comey earlier this month. And Trump has gained a reputation for his off-the-cuff candor, leading many to question whether he can be trusted not to reveal national security information.

How does the process work, and why does it exist at all? The process is flexible, and the history is borne of geopolitical caution, according to new reports, public information and interviews with David Priess, who served as an intelligence officer during the Bill Clinton and George W. Bush administrations, as well as other intelligence officials who wished not to be named.

Why do the candidates receive briefings?
When President Franklin Roosevelt died in April 1945, then Vice President Harry Truman assumed the role of commander-in-chief without ever having been briefed on the existence of the atomic bomb or the developing situation with Soviet Russia. “I felt like the moon, the stars, and all the planets had fallen on me,” he told reporters at the time.

In an effort to spare future presidents a similar celestial burden, Truman instituted a process of offering intelligence briefings to all candidates, beginning in 1952.

Today, the motivation for the briefings has shifted, said Priess, author of The President’s Book of Secrets, which chronicles the history of presidential intelligence briefings.

“They want to make sure that, inadvertently, the candidate doesn’t say something that damages national security initiatives for the sitting president,” Priess told TIME, adding that briefings are also intended to stop presidents-to-be from saying something that conveys their ignorance.

Who receives the briefings?
Briefings are given to presidential and vice presidential candidates and one or two trusted staffers. Director of National Intelligence James Clapper confirmed on Thursday that both Clinton and Trump would be offered classified national security briefings. “I’ll tell you really it’s not up to the administration and certainly not up to me personally to decide on the suitability of a presidential candidate,” he said, declaring that voters render someone qualified through the nomination process—although the tradition falls under the authority of the sitting president.

“There’s a long tradition that the intelligence community at the appropriate time—and now is the appropriate time since both candidates have been officially anointed—that both camps will be reached out to and offered briefings,” Clapper said Thursday.

Priess said there have been several candidates since 1952 who haven’t received a briefing, either due to scheduling challenges or because they declined, as Barry Goldwater did in 1964 and Walter Mondale did in 1984.

Depending on candidate interest, the briefing could be a one-time event or multiple briefings, up through the November election.

Could Trump or Clinton actually be denied a briefing?
It would take a “real tectonic shift in a campaign” for that to happen, Priess said, adding that some thought Trump’s comments about Russia this week—in which he encouraged the country to hack into Clinton’s Secretary of State emails—qualified as that kind of moment.

There is nothing to stop the sitting president from denying a briefing or withholding certain information from a briefing, but Priess said it’s unlikely President Barack Obama would interfere with either, especially because he has said he’s delegated decisions about the briefings to Clapper.

Priess said intelligence officials striving to be “scrupulously neutral” provide the same information to both candidates regardless of party affiliation.

“It’s also unprecedented for a candidate not to be offered an intelligence briefing for perception of appropriateness,” he said.

While Priess said concerns about information leaks are reasonable given the controversies surrounding the current nominees, he thinks it’s unlikely a candidate would make that mistake: “As a general rule, it’s like Vegas.” While legal consequences are “extremely unlikely” in the event a candidate talks, he said there would still be “huge ramifications” politically.

“It makes little strategic sense, and it makes little political sense, to reveal what you hear in these briefings,” Priess said. “I would find it hard to believe—based on precedent and based on logic—that there is a dire national security threat of someone going out and repeating what they were told in a briefing.”

What is included in the briefing?
In the past, the briefings have traditionally included top-secret information and SCI (Special Compartmented Information) material. It’s not yet clear whether that will be the case this time.

The candidates are briefed on broad national security themes, such as terrorism, and given information about specific countries, such as China, Syria and Russia. They are allowed to ask for more detail. They are not briefed on covert actions or ongoing operations nor on the identities of foreign agents providing the information used in the briefings. “These are not the crown jewels of the United States intelligence community,” Priess said.

In general, the briefings are a discussion—not given in the form of briefing books, although information is sometimes supplemented by handouts and graphics.

Clapper described the briefings as a broad overview. But Priess cautioned against downplaying their impact. “We shouldn’t delude ourselves into describing it as a general, generic briefing,” he said. “Let’s not look over the fact that it is a top-secret, classified briefing.”

What about a third-party candidate?
The briefings are a courtesy, with no statute specifying who may receive them. This year, in particular, it’s possible third-party candidates could be included, Priess said, noting that the two-party system has fallen out of favor with many voters this cycle.

That’s left an opening for Green Party candidate Jill Stein and Libertarian Gary Johnson, who has received the support of 13% of voters in recent polls—a figure that puts him close to qualifying for general election debates. (In order to qualify, Johnson will need the support of at least 15%, according to an average taken from five selected national public opinion polls ahead of the first debate.)

Read more: Can Libertarian Gary Johnson Be a Factor in 2016?

“There’s a strong case to be made that yes, Gary Johnson should be brought into the loop, if only to limit the perception that the briefings themselves are partisan,” Priess said. “If there’s ever a good time to reform the system for providing intelligence briefings to candidates, it’s now.”

Third-party candidates have been included previously. Independent candidate John Anderson received briefings in 1980, and American Independent Party candidate George Wallace received them in 1968, Priess said.