Whoever sets the president's agenda possesses a great deal of power. Often, that role belongs to the major political parties, or the president's most immediate set of advisers—but Trump's relationship with both is tenuous at best.

Donald Trump fields a question during the first Republican presidential debate hosted by Fox News and Facebook at the Quicken Loans Arena on August 6th, 2015, in Cleveland, Ohio. (Photo: Scott Olson/Getty Images)

In last week's Slate Political Gabfest, the participants discussed a recent collaboration by 60 Minutes and the Washington Post about the opioid epidemic. That piece alleges that, after significant lobbying, Congress weakened the Drug Enforcement Agency's ability to go after irresponsible drug distributors, actually worsening the opioid crisis. The Gabfest participants, particularly John Dickerson, host of Face the Nation and political director of CBS News, wanted to know why President Donald Trump wasn't making more of this issue.

It's an excellent question. The opioid crisis is an issue that Trump ran on, and it's one that particularly affects the downscale rural whites who supported him so strongly last year and for whom he's tended to advocate. And, in many ways, it would be a very easy issue on which he could make some political hay. He's not responsible for the problem, it gives him a chance to criticize Congress and goad them into action, and, unlike many of the things he complains about, it is actually happening. It would be a chance for him to take a popular and populist stance on a legitimate public-health crisis.

Trump may well pivot to this issue in the coming days or weeks. However, I'd like to suggest a reason why he didn't jump all over this when the 60 Minutes episode aired: It wasn't on Fox.

I strongly recommend reading through Matthew Gertz's Twitter thread in which he watched Fox & Friends while following Trump's Twitter feed. Basically, approximately 30 minutes after a Fox story, Trump would tweet something related to it. Fox called congressional Democrats obstructionists at 6:08 a.m. on October 18th, and Trump tweeted that Democrats are opposed to his tax reductions 30 minutes later. Fox ran a story about James Comey at 6:29 a.m., and Trump tweeted a criticism of Comey 27 minutes later. This pattern continues. (The president TiVo-ing Fox & Friends helps account for the time lag.)

Gertz is not the first person to notice this pattern, although the collection of tweets is very helpful. We know Trump watches a lot of Fox. He tends to adopt its perspectives on the news. Indeed, it often seems that all the knowledge and background he gets on a subject comes from Fox commentators.

No, he doesn't exclusively watch Fox. We know (from his complaints) that he watches CNN occasionally and (from his complaints) that he at least glances at the New York Times. But Fox seems to drive his attention.

Presidential scholars will tell you that the presidency is a constitutionally weak position, but that one of the major strengths it has is setting the agenda for the federal government. No one can compete with the media attention the president will receive, and what he decides will be an important issue often ends up becoming so; whoever sets the president's agenda possesses a great deal of power. Often, that role has fallen to the major political parties, but Trump's relationship with his party is a tenuous one. Sometimes it falls to the president's most immediate set of advisers.

In Trump's case, it appears to be Fox News. The news network devoted to covering the federal government is, in fact, setting that government's agenda. Reporters and news outlets have occasional had some sway with the president, but it's hard to think of a parallel to this relationship. Indeed, this helps to explain why the Republican agenda has been so fraught and disorganized.

So, back to the opioid crisis question. I obviously cannot prove this, but imagine if the story reported by 60 Minutes and the Washington Post had actually been discussed, at length, on Fox & Friends. They'd naturally add their own spin—e.g.: this was a crisis that Congress worsened while President Barack Obama sat back and did nothing. My guess is that Trump would have been all over the story within minutes. He'd have been tweeting relentlessly and calling Mitch McConnell and Paul Ryan and demanding that they address this issue immediately. And then he'd claim he was the first president to fight a war on drugs.

Now, this would last only so long, of course. He'd soon (possibly within a few hours or less) become distracted by something else. But at least for a while, he'd be doing the things that presidents normally do—trying to make good on a campaign promise and direct federal action at an existing public policy problem.

This is a lot of pressure to put on Fox, which is notably not a policy shop. It's a news network with a primary mission of stoking and directing outrage. This is a substantial mismatch between expertise and role. But then that sort of thing seems to be common this year.