Trump's Long Relationship with Twitter.
BOLDUAN: President Trump has a long relationship with Twitter. As a businessman, he used Twitter to promote himself and his projects. As a candidate, Candidate Trump used Twitter to rally supporters. And as president, he still tweets and tweets and tweets, of course. Watch this.</s>BILL WEIR, CNN CORRESPONDENT: When it comes to American adversaries and Pyongyang or Moscow, following Donald Trump on Twitter, what worries you the most?</s>GEN. MICHAEL HAYDEN, FORMER CIA DIRECTOR & FORMER FBI DIRECTOR: If I'm the head of a hostile or even a friendly intelligence service, I've got a new office over here. Follow that account. Tell me what this man is saying. It's tremendously revealing. We know the president's hot buttons, his vulnerabilities, what upsets him. We know what he demands from his subordinates, loyalty. We even know his sleep patterns based upon his Twitter usage.</s>WEIR: Right.</s>HAYDEN: That's a tremendous gift to a foreign member.</s>WEIR: All of those things somebody like Vladimir Putin, say, takes great pains to hide?</s>HAYDEN: Oh, of course. Because you don't want to advantage the other guy.</s>WEIR (voice-over): While lashing out at the "Washington Post," this tweet declassified a top-secret operation to arm Syrian rebels. Intentional or not, it's the kind of revelation that makes jaws drop in the capitols of both enemies and allies.</s>STEVE HALL, RETIRED CIA CHIEF OF RUSSIA OPERATIONS: I can guarantee you that there are liaison services right now, services that work with us, foreign intelligence services, who have probably decided to do a little self-editing, and we just don't know what he' going to do.</s>WEIR (on camera): They're withholding valuable information from the</s>U.S. HALL: I believe --</s>WEIR: -- out of the fear he might tweet it?</s>HALL: I believe that's probably -- probably happening.</s>BOLDUAN: This is already raising questions in my mind. With me now, the man behind this special report, Bill Weir.</s>WEIR: He, Kate. Good to see you.</s>BOLDUAN: Thank you for bringing me the gift.</s>WEIR: A little light reading right here. These are all the president's tweets. They seem so temporary, all the digital musings, but these will be studied as the sign of our times for centuries.</s>WEIR: It's pages.</s>BOLDUAN: It's pages. It's several thousand.</s>WEIR: Yes, 1,313 pages.</s>BOLDUAN: Yes. And back here, just the tweets since becoming the 45th president of the United States. But it's so enlightening when you go to the beginning and see how it evolved, how he learned to weaponize it, when he first started attacking Barack Obama. And we talked to supporters, like Scott Adams, the "Dilbert" cartoonists, historians, spy chiefs, as you saw there, about the cost benefit of our first Twitter president.</s>BOLDUAN: When you really -- we all follow his Twitter feed. What really surprised you when you started digging into this?</s>WEIR: Just how you can see a couple weeks after that infamous White House Correspondents' Dinner heckling from Barack Obama is when he started launching attacks. It's almost this timeline of how aggressive they got. He would try lines. He tried, "We have to make American great again, the day after Barack Obama won re-election," which few people noticed at the time, but is a seminal moment in American history right now. And we also talked to a data scientist who did sentiment analysis. Based on the aggressive nature of the language, you can tell which were sent from his campaign staff, which were sent from him. But he has tweeted himself in the foot. We examined what exactly he gets out of this and whether it will ever stop.</s>BOLDUAN: And does it -- everyone you talked to, did they give a sense of what this means for the next guy or gal? What this means for the next president?</s>WEIR: Yes. If you look back in presidential history, the ones we remembered didn't re-invent the form. Right? FDR wasn't the first in radio but he re-invented it. Barack Obama was really the first Twitter president, came under his. But Trump has defined himself. So social media going forward in politics, there's no putting that toothpaste back in the tube. Right? Whether somebody does it as combatively as this man, this sort of fire hose, raw unfiltered id, seemed unlikely.</s>BOLDUAN: It's also fascinating, the more criticism he gets, he seems the more defiant he is about his Twitter.</s>WEIR: Exactly. It goes back -- I think, it's in his DNA. His father, Fred Trump, raised him to believe the worst thing than bankruptcy is obscurity. His father used to drop leaflets announcing his building projects over the city. It's like the early tweet? Right?</s>BOLDUAN: Can't wait to see it. Great to see you, Bill.</s>WEIR: Thanks, Kate.</s>BOLDUAN: Some light reading for this weekend.</s>WEIR: Exactly.</s>BOLDUAN: Watch this CNN special report, "Twitter and Trump," tonight 9:00 p.m. Eastern right here on CNN. Coming up for us, we're following breaking news out of Barcelona. A manhunt underway for the driver of the van that plowed into that crowd yesterday afternoon killing 13 people. More than 100 injured still. Why the terror cell may be bigger than first thought. Be right back.