ROBERT SIEGEL, HOST:
Let's turn to presidential politics and the tradition of giving candidates top-secret intelligence briefings. The practice dates back more than 60 years, but it's proving especially controversial this election cycle, as NPR's Mary Louise Kelly reports.
MARY LOUISE KELLY, BYLINE: Imagine what it must've felt like to be Harry Truman back in 1945. He'd been vice president for a mere 82 days when Franklin Roosevelt died. Truman suddenly inherited the presidency, World War II and a huge secret.
DAVID PRIESS: He didn't even know the atomic bomb existed. He didn't know about the Manhattan Project.
KELLY: That's David Priess, author of "The President's Book Of Secrets," a history of the president's daily brief. Priess says by 1952, Truman had made up his mind that his successor should assume the Oval Office better prepared than he had been, so he offered classified briefings to each of the nominees, a tradition that's held ever since. Not everyone accepts the offer. Walter Mondale turned it down in 1984 before losing in a landslide to Ronald Reagan.
Priess, a former CIA presidential briefer himself, says the typical practice - and the way things will likely unfold this summer - is for candidates to wait until the Republican and Democratic conventions. But that's not always the case.
PRIESS: Jimmy Carter, who had no experience with foreign intelligence as governor of Georgia, asked for and got his intelligence briefing before his party even nominated him.
KELLY: Who makes that call on who gets briefed and when he could start?
PRIESS: Ultimately, it's the president's call.
KELLY: Meaning the sitting president and, in this case, Barack Obama, which does not mean the candidates will see everything Obama has access to. Details about covert actions, for example, and sensitive nuclear programs will almost certainly be held back. That's the way it's always done. And this year, it will be especially critical for intelligence briefers to exercise discretion, says Aki Peritz. Peritz is a former CIA analyst. He is one of several intelligence officials sounding alarm bells about the prospect of sharing the nation's secrets with Donald Trump.
AKI PERITZ: He's never held public office before. He's a business developer and a reality TV star. So if the United States starts giving Donald Trump classified briefings, it could be a disaster.
KELLY: Aki Peritz calls Trump, quote, "a man famously without filter." And Peritz says he worries there's little to stop Tromp or any other candidate from, as he puts it, blabbing on the campaign trail.
PERITZ: The Department of Justice could bring charges against you, but it's a very, very high bar for the attorney general to bring the boom down on a presidential candidate in a presidential year. It's never occurred, ever.
KELLY: It is worth noting that the ability to protect classified information has already been an issue this campaign. Not because of Trump, but because of his likely Democratic opponent, Hillary Clinton, and her use of a private email server back when she was secretary of state. Over the years, Clinton has been privy to thousands of classified briefings. In an interview last week, Trump told The Washington Post he's eager to start receiving them.
Meanwhile, James Clapper, the director of national intelligence, has shared a few details about how this summer's briefings might unfold. At a recent breakfast with reporters, The Daily Beast pointedly asked Clapper what steps he is taking to ensure candidates won't mishandle classified information. Clapper replied that the process is designed...
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JAMES CLAPPER: ...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.
KELLY: Clapper added that the top-secret briefings will be held in a secure facility at whatever date and time is most convenient for the nominees. Mary Louise Kelly, NPR News, Washington. Transcript provided by NPR, Copyright NPR.