Why it Takes 40 Calls to Get One Person to Answer an Election Poll

One day Republican Donald Trump is up in the polls. The next day, Democrat Hillary Clinton outpaces him. What makes the difference? The science of data collection in the U.S. has changed over the years. But the results still vary, depending on who conducts the poll and how it is conducted. VOA’s Carolyn Presutti brings us a rare look inside a polling location in Pennsylvania to reveal how polls are done.