After Donald Trump is formally chosen as the Republican presidential nominee, he’ll be able to receive classified U.S. intelligence briefings, which could include some of the same sensitive information that President Obama is given in the Oval Office.

And that prospect has some spies sweating. Trump, who can’t seem to dam his stream of consciousness on Twitter, and who has lately taken to spreading rumors and conspiracy theories on national television, has never been privy to national secrets. Nor has he ever demonstrated that he’s capable of keeping them.

“My concern with Trump will be that he inadvertently leaks, because as he speaks extemporaneously, he’ll pull something out of his hat that he heard in a briefing and say it,” said a former senior U.S. intelligence official who has participated in the process of briefing presidential candidates.

Unlike his presumed rival, former Secretary of State Hillary Clinton, who would receive the same briefing if she’s the Democratic Party nominee, Trump has never sat across the table from U.S. intelligence analysts and been given updates on the latest machinations of ISIS, or efforts by foreign governments to penetrate American computer networks. He also has selected a team of largely unknown advisers who might have trouble helping him to contextualize what he might hear and know what questions to ask. (Of course, Trump isn’t under FBI investigation for potentially spilling secrets from his private email server, like his Democratic rival.)

Trump’s improvisational public speaking style, coupled with his penchant for making unverified—and unverifiable—claims, could make for especially tense sessions. Presidential candidates are given their briefings in highly-secured facilities, in part to impress upon them the sensitive nature of what they’re hearing.

“It’s not an unreasonable concern that he’ll talk publicly about what’s supposed to stay in that room,” said another former senior intelligence official.

A currently serving U.S. official echoed some of those anxieties and wondered whether Trump would respect the discretion of the briefing and not use it to his advantage on the campaign trail.

The current and former officials asked to speak anonymously in order to express their concerns about the upcoming briefings.

Spokespersons for the Trump and Clinton campaigns didn’t respond to requests for comment.

Presidential nominees have received classified intelligence briefings since 1952, when President Harry Truman authorized the CIA to share information with Dwight Eisenhower and Adlai Stevenson. Upon assuming the presidency after the death of Franklin Roosevelt in 1945, Truman had been surprised to learn how many details about national security had been withheld from him as vice president, and he wanted the incoming commander-in-chief to have a head start on a steep learning curve.

“The practice of providing intelligence briefings to the presidential nominees of both parties is a sound one,” Rep. Adam Schiff, the top Democrat on the House Intelligence Committee, told The Daily Beast. “Whether it is premature in the case of Donald Trump is one question; whether it would do any good is another.”

For their part, the spies who’ll actually be sharing secrets with Trump and Clinton—presuming they’re ultimately the nominees—have been busy preparing for meetings that could take place as soon as the conventions are wrapped up.

“We have already established a plan for briefing both candidates when they are named, and certainly after the November when the president-elect is known, and it gets more intensive,” Director of National Intelligence James Clapper said in response to a question from The Daily Beast at a meeting with reporters in Washington last week.

Asked what precautions the intelligence community would take to ensure that any classified information the candidates received was not mishandled, Clapper said that the briefings, per custom, would be given in a secure facility wherever it was most convenient for the nominees, and according to their schedule. In 2008, Sen. Barack Obama was briefed by Director of National Intelligence Mike McConnell at an FBI building in Chicago, the city where he also had his campaign headquarters.

Clapper said that his office had already set up a team to prepare the briefings and that a “designated lead,” who is not a political appointee, is running the effort.

Once a briefer is chosen to meet with the nominees, the intelligence director’s office will “oversee [the process] to ensure that everybody gets the same information and that we do comply with the needs to protect sources and methods and comply with security rules.”

The nominees, in that sense, are on an even playing field. Trump and Clinton would receive the same information, a sort of sanitized version of the President’s Daily Brief, which lays out various national security threats and concerns and areas of interest. But it will be stripped of the most sensitive information about ongoing operations or covert programs, officials and experts said.

“They’ll get a top secret briefing, but it won’t contain code word information,” said Tim Naftali, an intelligence expert and professor at New York University. “And I doubt they’d be getting any information about nuclear weapons. But it will be a discussion of the world, threats to the nation, how the war in Syria is going.”

Immediately after the election, the president-elect would likely be privy to the same information the current commander-in-chief sees. His or her staff will begin moving into presidential transition offices that have been outfitted with secure rooms and computers. One former official said that on the night of the 2012 election, there were representatives from Gov. Mitt Romney’s national security team waiting near a transition office in Washington to begin getting the Republican nominee up to speed should he be elected.

But from nomination to election to inauguration, it’s ultimately the president’s call how much information the rivals for the Oval Office get to see. He can dial up or down the amount of classified information. So long as both Trump and Clinton see the same things, Obama could effectively limit each of them to benign information that’s less revealing that what they might read in a newspaper.

George W. Bush, who directed that Obama and his opponent, Sen. John McCain, get comprehensive briefings on the campaign trail, still withheld information that revealed the sources and methods of intelligence activities, as well as information about covert operations, said Martha Kumar, a historian and author of Before the Oath, a book on the Bush-to-Obama transition.

Some of Bush’s prohibition extended even to President-elect Obama.

Steve Hadley, who had served as Bush’s national security adviser, told Kumar that the president felt sources and methods information was more than an elected president needed to know before he formally took office.

“When the man comes in and is president, sitting in this chair, that’s time enough,” Bush said.

The candidates have some say in the process as well, namely, how many briefings they want to receive. Historically, many of them have found the demands of the campaign trail too consuming to take the time out to and sit in a secure facility. The candidates also cannot take staffers who don’t have the proper security clearances into the room with them.

Nafatali said he’d be surprised if Trump in particular wanted more than one, customary briefing.

“Politically, I think for many candidates, it’s better that they don’t know things,” Naftali said. “They might realize how vacuous their foreign policy thinking was.”

Trump has made a pillar of his candidacy the argument that the Obama administration has utterly failed to counter its strategic rivals, from ISIS to Russia to China.

“Once candidates get secret information, they realize that there aren’t answers for every problem, but they also discover that the U.S. government is not neglecting all these problems,” Naftali said. “It makes some of their arguments on the stump completely hypocritical.”

For Trump, the temptation to blab about what he learned in a classified briefing might be great. But the smarter move might be to nod politely and forget what he heard.

Updated 10:45 a.m. on 5/5/16 to add quote from Rep. Adam Schiff, the top Democrat on the House Intelligence Committee.