About a month after the 2016 election, Breitbart News posted an article, “The Deep State vs. Donald Trump,” where an anonymous contributor (assumed to be Steve Bannon) describes a “deep state” made up of thousands of bureaucrats stretching across the whole of the federal government, all universally committed to undermining a Trump presidency. At about that same time, President Trump used the term "fake news" on Twitter for the first time and would repeat some variation of the "fake" mantra over 400 times by early 2018.
While the “deep state / fake news” narratives seem to cover different ground, they are based on the same technique, a form of preemptive ad hominem, commonly known as poisoning the well - discrediting your opponent to an audience in advance, in order to encourage dismissing any future claims or accusations they may make against you.
. If ad hominem is a way to deflect criticism and scrutiny, then poisoning the well is a way to insulate oneself from criticism and scrutiny in advance. Both the “deep state” and “fake news” narratives effectively prime an audience for any criticism or accusations of wrongdoing that might be uncovered thereafter by government oversight or news organizations. By proactively selling these narratives, any scrutiny from either can be reflexively cast aside as politically motivated and written off as nothing more than rogue bureaucrats or biased news outlets pursuing their own personal agendas.
Like all ad hominem attacks, poisoning the well does this by shifting the focus from the actual argument to the one making the argument, allowing the accused to avoid scrutiny and shift the narrative to his advantage. It devalues all other opposing views, reinforcing the pull of the propagandist, and encouraging listeners to simply dismiss those views, and voluntarily cede their channels of information.
Poisoning the well is particularly effective when the narrative is plausible in context. Both the “deep state” and “fake news” narratives are empowered by the sprawling, diverse nature of these institutions. Government bureaucracy is vast and expansive, confusing, and often intimidating. Likewise, most news organizations are owned by a handful of large, multi-national corporations and can seem equally all-powerful and intimidating. Appealing to these anxieties is a reliable way to stoke conspiratorial narratives. And those who contradict those narratives frequently run the risk of being portrayed as gullible or complicit.
This isn’t helped by an American public whose trust in the government and the media is at an all-time low. In September 2020, Pew Research found that just 20% of Americans trust the federal government to "do the right thing" always or most of the time. Another Pew study, from August 2020 found that “no more than half of U.S. adults have confidence in journalists to act in the best interests of the public,” and while 61% of Americans “expect the news they get to be accurate,” nearly 69% “think news organizations generally try to cover up mistakes when they do happen.” 
This underlying distrust in the government and media makes Americans uniquely predisposed to accepting a “deep state” conspiracy or to writing major news organizations off as “fake news.” It makes it all-the-more believable that these immense and splintered ecosystems could somehow be coordinating behind the scenes and working in unison towards the uniform secret agenda. By effectively poisoning the well, politicians can isolate audiences and prime them for even bigger lies in the future; a future where they are free from oversight and accountability.