Are opinion polls accurate? Did they miss the rise of Donald Trump and Bernie Sanders? Do they properly measure America's increasingly sharp political and cultural divisions? What's the difference between a well-designed poll conducted with careful methodology and a sloppy opt-in online survey?

Our guest is Gary Langer, an internationally recognized opinion researcher and longtime director of polling at ABC News. He has overseen and analyzed more than 750 surveys on a broad range of topics.

Gary has a passion for numbers and explains what listeners should know about polls. He tells us that surveys were taken at least a year ago - when many pundits dismissed Trump as an outlier - clearly showed that his views on banning overseas Muslim visitors and building a wall along the border with Mexico had substantial support among Republican voters. Trump led the GOP field throughout the lead-up to the primary season.

"The news media have for far too long indulged themselves in the lazy luxury of being both data-hungry and math-phobic," Gary tells us. "I would suggest polls are anti-pundit. A good quality poll ... holds a pundit's feet to the fire "

In this episode, we get some vital takeaways on how well-researched randomized polls are conducted and what changes have been made recently to ensure that a representative sample is reached.