It’s been another challenging season for the broadcast networks. Between the presidential election and the continued shift in viewing habits, all of them except NBC are down this season in the all-important adults 18-49 demo (NBC, which is No. 1 in the demo this season, is even with last season.) But a few standout new shows—particularly This Is Us—are giving them hope for the future. The five broadcast chiefs talked with Adweek about the biggest lesson they’ve learned so far this season:

"You never know where a hit is going to come from, and you can't strategize your way into it." Robert Greenblatt, chairman, NBC Entertainment

“You never know where a hit is going to come from, and you can’t strategize your way into it. You can’t formalize a process that figures out how to check off the boxes so you just can manufacture it. It’s the old-fashioned thing of, the timing is right, the creator has an idea that he’s passionate about that hits the audience at a certain place. It fills a void that we didn’t even know was open. All those things that in hindsight you go, ‘Oh yeah, that makes sense why that worked,’ but you can’t see in front of it. This Is Us is the great example of that. We weren’t in the market for a show like that; it was Dan [Fogelman, the creator] with an idea that we immediately sparked to and then we built it the old-fashioned way. It’s got no stars in it. It’s just good casting. And the finished product was extraordinary.”

ABC Entertainment president Channing Dungey: “For me, coming to the end of the first year on the job, just how difficult it is in terms of putting a schedule together. Anybody that grows up in creative, you play armchair scheduler as you go, and when you’re actually sitting in this seat, and every decision that you make has real creative and financial repercussions, it’s much more complicated. Particularly in this day and age, where we’re living in a multiplatform universe. We as a broadcast network have linear schedule demands to look at, but then you also want to look at how the audiences are watching the shows, and when they’re watching them, and all of those pieces playing together. That was the biggest lesson and biggest challenge.”

The freshman hit This Is Us was "built the old-fashioned way," said NBC's chief.

“The biggest surprise to me, from a programming point of view, is that NBC did a remarkable job with This Is Us. Also, the growth of that audience, because you would have thought it would have headed down the direction of Parenthood, as opposed to the other way. So kudos to them; they deserve credit.”

CBS Entertainment president Glenn Geller: “For me, it’s that you have to remember who your audience is. You have to give them the kinds of programming they like, while also taking swings. And I think we’re able to do that. Superior Donuts is a comedy that fits right in our wheelhouse. And yet, it certainly is going to take a swing in terms of its subject matter. Those are the kind of shows I want to put on, and I think it keeps in mind who are audience is and what they want to watch, while also pushing it a little bit. We have the No. 1 new drama [in total viewers] with Bull and the No. 1 new comedy [in total viewers, with Kevin Can Wait]. That doesn’t happen by guessing what the audience wants. It happens because we really pay attention to what we develop and how we schedule our programs.”

Fox Television Group chairman and CEO Dana Walden: “I look at the fall and look at a business of launching so many shows in this truncated period of time, where viewers just can’t possibly sample all of the great content that’s being platformed in a short period of time. All of us looked at our schedules this year and saw, between the Olympics, the presidential debates and the election, that fall was such a challenging time to launch something new. And what I have learned in this job is the ultimate need for prioritization. You have to lock in to a show and send a message, and NBC did that incredibly successfully with This Is Us. They didn’t endeavor to launch eight shows; they sent a pretty powerful message about one and their audience responded. So I have learned again about priorities, and the power of broadcast.”