President Donald Trump's favorite news channel has been, for the longest time, Fox News. But cracks have begun to emerge this year.Fox News' opinion hosts, like Sean Hannity and Tucker Carlson, usually support Trump, but the channel's independentnews division and polling system aren't beholden to his whims.More and more, when Trump doesn't like what he sees, he's prone to lashing out in a very public way, usually with a storm of fiery tweets.Visit Business Insider's homepage for more stories.President Donald Trump values loyalty.He expects it from his allies, his employees, and his supporters. When he doesn't get it, or feels disrespected, he's prone to lashing out in public, usually via Twitter.Fox News, Trump's favorite news channel, was part of what propelled him to victory in 2016. His frequent appearances won over the hosts of "Fox & Friends" in the mornings and the opinion programs during primetime.But as Trump has come under scrutiny for pressuring a foreign government to investigate his rival, the president hasn't received blind loyalty from his preferred network. While Fox News' opinion hosts still stand behind Trump, its news division and its polls are independent.In the last year, and particularly as the impeachment inquiry has heated up, Trump has regularly let the news channel know, usually through Twitter, when he doesn't like what an anchor says, who a particular guest is, or what their polling concluded.Here are all the times the president has criticized Fox News. The network didn't respond to Business Insider's request for comment.SEE ALSO:21 people who have gone through the revolving door between Fox and the Trump administrationDON'T MISS:Trump bashed Fox News' Chris Wallace, saying he'd 'never be his father,' after Steve Scalise's contentious interviewTrump has had a flourishing relationship with Fox News. The news channel touted him as a potential presidential candidate long before he announced he was running. And since becoming president, he's appeared on the news channel more than 40 times. In contrast, since taking office, he's never appeared on CNN.Sources: The New Yorker, Politico, USA Today The first flare-up with Fox News came during the network's presidential debate during the 2016 election. When former anchor Megyn Kelly asked him about sexist comments he'd made, Trump took it personally. He went on a prolonged attack against Kelly, calling her sick and overrated. Fox News even released a statement about it, saying he had an "extreme, sick obsession," with her that was "beneath the dignity of a presidential candidate."Sources: Politico, Business Insider, TwitterThings have become more strained in 2019. In January, Trump attacked Fox News correspondents John Roberts and Gillian Turner. He said they had less understanding about "the wall negotiations," than reporters at CNN and NBC, two media institutions Trump is not fond of.Source: USA Today In March, he attacked Fox News anchors Arthel Neville and Leland Vittert, asking on Twitter if they had been trained by CNN, and saying they and Shepard Smith should work there instead. But it wasn't clear why he was criticizing them, because Fox News was playing a rerun of "Fox News Sunday" at the time of the tweets, which those anchors weren't on.Sources: Deadline, The HillIn April, he criticized the decision to host a town hall with Democratic presidential candidate Bernie Sanders. He tweeted that it was "so weird," to watch Sanders on Fox News, adding that it wasn't surprising to see the audience and Fox News anchor Bret Baier being so "smiley and nice."Source: Vox In May, he criticized Fox News for doing the same again with Democratic presidential candidate Pete Buttigieg. Trump tweeted, "Hard to believe @FoxNews is wasting airtime on Mayor Pete, as Chris Wallace likes to call him. Fox is moving more and more to the losing (wrong) side in covering Dems."Source: Politico In May, he also retweeted a tweet that criticized Fox News' legal analyst Andrew Napolitano, saying he had made multiple incorrect statements, and called for him to be taken off the air. It came in response to Napolitano calling Trump "immoral" and "repellent."Source: The Daily Beast In June, Trump tweeted, "something weird going on at Fox," in response to a poll the network released, which showed him trailing five Democrat candidates in a hypothetical presidential match-up. He said polls were always bad for him.Sources: Politico, The Hill On July 7, Trump attacked Fox News' weekend anchors, saying they were worse than CNN, or "lyin' Brian Williams," because Democrats were appearing on their shows.Source: Politico Later that day, he criticized Fox News for hiring Donna Brazile, a former CNN analyst and head of the Democratic National Committee. He tweeted that it was impossible to believe they had hired her, after she was fired by CNN, "for giving Crooked Hillary Clinton the questions to a debate."Source: PoliticoAnd finally, at the end of a busy day of Twitter, he tweeted that Fox News had "forgot the people who got them there."Sources: Politico, The HillOn August 7, he declared he even preferred to watch "Fake News CNN" over Fox anchor Shepard Smith, which could be one of Trump's harshest insults.Source: The New York Times On August 15, a Fox News poll had him sitting below 40% for preferred president. Three days later he told reporters, "Fox has changed. And my worst polls have always been from Fox. There's something going on at Fox, I'll tell you right now. And I'm not happy with it."Source: VoxOn August 18, Trump attacked Democrat Juan Williams, who is one of the hosts on "The Five," calling him "pathetic," "nasty" and "wrong."Source: Vox On August 28, he criticized Fox News' Sandra Smith for what he considered "heavily promoting," the Democratic party, and giving "zero pushback" in an interview with Democratic National Committee communications director Xochitl Hinojosa. In those tweets he also managed to criticize Donna Brazile, Juan Williams, and Shep Smith.Source: Vox That same day he tweeted, "I don't want to Win for myself, I only want to Win for the people. The New FoxNews is letting millions of GREAT people down! We have to start looking for a new News Outlet. Fox isn't working for us anymore!"Sources: Twitter, VoxIn late September, Trump took aim at Fox News' Ed Henry, who was interviewing conservative radio host Mark Levin. In 23 minutes, the president fired off or retweeted 23 tweets, several of which mentioned Henry should have been working at CNN.Sources: Washington Post, Politico On October 10, after Fox News released a poll that said 51% of voters wanted Trump impeached, Trump tweeted he had never had a good Fox News poll, and that the pollster "suck[ed]." He also returned to a familiar theme ' that the news channel had changed. He said it was, "much different than it used to be in the good old days."Source: Twitter In November, Trump took on "Fox News Sunday" host Chris Wallace, after Wallace interviewed Rep. Steve Scalise. Trump tweeted that Wallace was "nasty and obnoxious." And sticking to his nostalgia for a better Fox News, the president said the "dumb and unfair interview," would never have happened in the past.Source: Business Insider Click here to read full news..