The three function as a big propaganda machine.
According to the Fact Checker's database, the average daily rate of Mr. Trump's false or misleading claims is climbing.
The problem isn't just the number or flagrancy of the lies — for example, that Vladimir Putin and the Russians didn't intervene in the 2016 election on his behalf, or that the Robert Mueller investigation is part of a Democratic plot to remove him.
And it's not just that the lies are about big, important public issues — as when he says immigrants commit more crimes than native-born Americans, or that trade wars are harmless.
The biggest problem is that his lies aren't subject to the filters traditionally applied to presidential statements — a skeptical press, experts who debunk falsehoods, and respected politicians who publicly disagree.
Last week, at a joint press conference with British Prime Minister Theresa May, Mr. Trump refused to acknowledge a CNN reporter, saying, "CNN is fake news. I don't take questions from CNN." He then turned to a Fox News reporter, saying, "Let's go to a real network."
The word "media" comes from the term "intermediate" — that is, to come between someone who makes the news and the public who receives it.
Intermediaries hold officials accountable for what they say. Without them, the public has no way of judging the truth of a politician's statements.
But Mr. Trump doesn't respond to anyone who disagrees with him. He denigrates the mainstream press. And he shuns experts. So his lies go out to tens of millions of Americans every day unmediated.
Consider his rallies. Most TV and radio networks simply rebroadcast them, or portions of them, typically without comment.
Yet they're filled with lies. At his most recent rally in Great Falls, Montana, Mr. Trump made 98 factual statements. According to the Washington Post's fact checkers, 76 percent of them were false, misleading or unsupported by evidence.
Trump claimed that "winning the Electoral College is very tough for a Republican, much tougher than the so-called 'popular vote,' where people vote four times, you know."
The claim ricocheted across the country even though countless studies have shown that Trump's claims of widespread voter fraud and abuse are simply not borne out by the facts.
Or consider Mr. Trump's tweets. More than 50 million Americans receive them daily. They're also brimming with lies.
Recently, Mr. Trump tweeted that Democrats were responsible for his administration's policy of separating migrant families at the border (they weren't), and that "crime in Germany is way up" because of migration. (In fact, it's down.)
And then there's Fox News. Around 6 million Americans watch each day and relate what they see and hear to their friends and relations.
Fox News is no longer intermediating between the public and Mr. Trump. Fox News is Mr. Trump. Many of his lies originate with Fox News, and Fox News amplifies the ones that originate with Mr. Trump.
Fox News's Sean Hannity is one of Mr. Trump's de facto top advisers. Mr. Trump has just appointed Bill Shine, the former No. 2 at Fox News, as his deputy chief of staff for communications.
No democracy can function under a continuous bombardment of unmediated lies.
What can you do, other than vote Nov. 6 to constrain Mr. Trump?
First, you can boycott Fox News' major sponsors. Vote with your wallet and starve the beast. Get others to join you.
Second, you might attend Mr. Trump's rallies, as distasteful as this may be. You're entitled to attend. He is, after all, the president of the entire country.
Organize and mobilize large groups to attend with you. Once there, let your views about his lies be heard and seen by the press.
Third, you might write to Twitter and tell its executives to stop enabling Mr. Trump's lies.
As the New York Times' Farhad Manjoo suggested recently, Twitter's employees should be encouraged to make a ruckus -- as did Amazon workers who pushed the firm to stop selling facial recognition services to law enforcement agencies, and Google employees who pressured Google not to renew a Pentagon contract for artificial intelligence.
Twitter defines its mission as providing a "healthy public conversation." Let the company know that demagoguery isn't healthy.
Your vote on Nov. 6 is key, of course.
But as the political season heats up, Mr. Trump's lies are heating up, too. And they will sway unwary voters.
So you need to be active now, before Election Day — on behalf of the truth.
Robert Reich, a former U.S. Secretary of Labor, is professor of public policy at the University of California at Berkeley. His latest book is "The Common Good.” His documentary, "Saving Capitalism," is available on Netflix.