In the wake of the 2016 election, Donald Trump called polls unfavorable to him everything from “fake” to “phony”. The polls, of course, are neither, but that’s beside the point. Americans have become so collectively distrustful of polls, especially after they seemed to suggest Hillary Clinton would win the election, that the president’s attempts to discredit the practice entirely have gained real traction.

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That’s where Anthony Salvanto, director of elections and surveys for CBS News, comes in. In his new book Where Did You Get This Number? A Pollster’s Guide to Making Sense of the World, Salvanto begins on election night, the events of which surprised him less than they did most Americans. He proceeds, in digestible and timely fashion, to demystify the world of polling and pollsters. Salvanto spoke to the Guardian about how we ought to think of political campaigns, his strategy for the upcoming midterms and why you’re probably represented in a poll even if you’ve never been asked to take part in one.

What’s the biggest misconception about polling you set out to correct with this book?

I’d like people to read the whole thing to see all that a poll can tell you and demand that your pollster not just predict the world, but explain it. In 2016 polling, if you looked beyond the horse race, you saw that there were Republicans who were conservative and were hesitant about Donald Trump. But if they were to come back home, he would gain a lot of ground. And, in fact, they did. If you looked beyond the Democratic numbers for Clinton and saw that many of her voters had less enthusiasm, or that both candidates were personally disliked, you could see potential movement in the polls. I want to use that method in part as a way to say to everyone, “Demand that your pollster tell you all the things people are thinking and feeling and why,” and when you see that larger picture, you probably won’t be surprised by much.

You write that we ought to think of campaigns as “persuasion and marketing efforts, not races”. What do you mean by that?

In a horse race, the distance is run, never to come back again. Sometimes that analogy can mislead people because a campaign is a collective decision; in theory everyone could change their minds the day before the election. If we think of them as decision-making exercises among people we more easily come to grips with this idea of change and movement, because there isn’t a finite amount of time left. The other part, frankly, is that although aggregations of polls have their uses, and although I understand the temptation to see them as a shortcut, I want to push people to see beyond the top-line numbers. Knowing the leader, as I write in the book, is somewhat like thinking you know how a bottle of wine will taste just by knowing the price.

In the aftermath of Trump’s victory, the practice of polling was so antagonized that people forgot that the national polls turned out quite accurately. Still, like you say, national polls didn’t decide the race.

Any time we’re faced with a lot of information, we understandably look for a way to shortcut it. “Well, if they’re winning nationally surely they must win.” I worry that some pollsters could be repeating that problem this year because the analogous situation now is the national generic ballot for Congress. Look, American politics doesn’t elect nationwide. If people only look at the national generic ballot, and if pollsters overemphasize the national generic ballot, we could be in for another situation where a number is accurate but still misleading.

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You often get complaints from people who don’t see themselves reflected in a poll, or who’ve never been asked to participate in one. In the book, you explain how polls are constructed so that like-minded Americans are more represented than they think.

Polling has always had a problem in that it’s shrouded in mystery because you can’t watch it work. Even if I think a large cruise ship shouldn’t be able to float, I can look out my window and see it go by the Hudson river. But polling depends on this idea of sampling, which is hard to grasp because most of us learn from our day-to-day experiences. What we sometimes don’t realize is that we tend to socialize with people who are more like us than not. We’re often told: “No one I know agrees with that.” Well, you probably hang out with a lot of people like you. So what I try to do is get the reader to think about how you could be represented, and how all the people who aren’t like you could be as well.

Think about the popular movie that you don’t like, and yet it’s popular. Someone out there is seeing them. Think about the kinds of clothes that you would never wear but you see others wearing them. The fact is there are many different kinds of people out there, and the idea of representation means that even if we don’t call you, there are so many people like you, at least in the broad respect we measure in a poll. One of them will be in the poll and will answer the question just the same way you would have. I like to think there’s a power in that idea: that we share enough with enough other people that one of them can represent us. And those times you are called for a poll, you’ll represent all those people yourself.

But Americans, perhaps, are resentful of the idea of having been spoken for.

I think that’s a healthy thing. We all like the idea that we have a voice, because we all like the idea that we can make a difference. It can be off-putting to think that someone is speaking for us. That’s a big part of why I wrote the book. I certainly understand the skepticism, but I also try to point out the many ways that we in fact do think like pollsters, perhaps more often than we realize.

Would you have been inclined to write this book had Trump not won?

I decided to write the book almost immediately after the election. I’ve always wanted to try to explain how polling works to a general audience in a way that’s accessible. I really feel like we need to explain ourselves to a general audience. It’s not about the numbers; it’s the stories that the numbers tell. Having said all that, the 2016 election felt like a good jumping-off point because so many people, when they were asking me what happened to the polls what they were really asking is: do I understand the country as well as I thought? I thought the 2016 election became a really good jumping-off point because people were asking the right questions. Not just how were you off by one or two points, but they were asking about understanding people.

To the extent you’re willing to speculate, are Trump’s approval ratings any kind of bellwether for 2020? Or is that a fool’s errand in the way national polls often are?

I will happily say I don’t know what will happen in 2020. We know in historical terms that the president’s approval rating has been the most stable in his first year or two in office of anyone we’ve measured. So while other presidents have bounced up and down with events or with the economy, President Trump has stayed within just a few points of his rating. And there’s a reason for that: Democrats are almost universally opposed, and Republicans are almost entirely approving. So, with that, you have to ask yourself, “What does that measure really mean?” That’s one of the themes of the book. We can tell a story, which is that, over time, more folks who were considering supporting him at the beginning of his term have moved into the harder opposition. His supporters, in turn, have become even more steadfast. That hardening, at least with history as any guide, does suggest there’s very little room for movement.