Citation From the January 19, 2020, edition of CNN's Reliable Sources

BRIAN STELTER (HOST): For three years now, President Trump has used Fox News as inspiration, as affirmation, and as raw material for his tweets. What used to be so strange is now so common, you know, Fox & Friends will say something, and the president will say it 10 or 20 minutes later. So let me introduce you to a man who tracks this for a living. He is here to share his most recent numbers from 2019. Matt Gertz is a senior fellow at the liberal media watchdog group Media Matters for America, and he joins me now. So Matt, this is part of your beat. Every time the president tweets something, you go and try to figure out if he heard it on Fox News, is that right?

MATT GERTZ (MEDIA MATTERS SENIOR FELLOW): Yeah, I've been doing it since October of 2017. Sometimes he makes it easy for me; he will put the name of a host in the tweet or he'll be quoting something outright. Sometimes he's talking about one of the weird Fox obsessions that no other network is talking about, so that makes it clear. And sometimes I am sort of lining up the time and showing how a large number of tweets in a row all matched up with Fox's programming over the last couple of hours.

STELTER: Yeah, so you've been doing this for two years now. It's kind of like in the same way fact-checkers have found new importance in the Trump years, people who figure out where the president is getting his information have found new importance. Let's put up your 2019 data on screen. This is Trump's total live tweets by network. Last year, according to Media Matters, you found Fox News was the source for 559 of the president's tweets.

GERTZ: And that's just Fox News. There's another 98 from Fox Business, the sister network.

STELTER: From Fox Business, right. Right. Now, Media Matters is a liberal group. I describe it as an anti-Fox News group. Is that accurate? Is that fair to say?

GERTZ: I think it is fair to say that we are very harshly critical of Fox News. We spend a lot of time watching what they say and do, yes.

STELTER: You all oppose Fox News. But the point is, you try to get this data because why? Because you want people to know how influential Fox is?

GERTZ: Sure, and how much what they are saying is impacting the president of the United States and through him, our daily lives and the policies our government carries out.

STELTER: Do you think it's fair to say that right now, as the impeachment trial gets underway, the Fox firewall is holding very firm, very strong?

GERTZ: Absolutely. I think they have been strongly in the president's quarter. through all of this. In fact, if you look at the last few months as the Ukraine story heated up and as it turned into impeachment, the president really fixated on Fox's commentary. He is trying to catapult their propaganda into the mainstream, picking up quotes and arguments that they make and then telling all of his followers all about it.

STELTER: Yeah. A former White House aide once made the point to me that Fox is like a content creation engine for Trump. That, you know, what he sees in the graphics and banners, he takes video clips and he puts them on Twitter. So it's like Fox is creating content for him, even though they say that's not what they intend to do, it's what ends up happening.

GERTZ: Sure. And, you know, the point of a lot of Fox's programming is to rile up its audience, to make them very angry, so that they come back and watch more of those programs. So that's the impact that it's having on the president.

​STELTER: Sean Hannity this week said that​ MSNBC and CNN are ​“state​-​run TV.​"​ I​'​m curious of how you react​ed​ to that?

​GERTZ: ​I mean, I think this is a fairly common tactic that Sean Hannity uses. ​He sort of parries back comments that are made about him and his network to the other ones. ​I think he's trying to hide th​e​ sort of depth​s​ of the relationship that he has with the president. ​You know, he​ reportedly​ speaks with him virtually every night after ​his show​.​ He​ advises him​ -- the president advises him​ on particular ang​le​s to take on his show. ​He's been referred to as the shadow chief of staff of the White House. ​And just this week, we learn​ed that​ Paul Manafort​, the president's former campaign chair,​ had been trying to use Sean Hannity as a back channel to the president to let him know that he wasn​'​t telling Mueller's team too much about what the president had done.