How pollsters have adapted to changing technology and voters who don’t answer the phone

Pollsters have developed a range of methods for selecting who is asked to answer poll questions. Guido Mieth/Moment via Getty Images

As the U.S. presidential election approaches, news reports and social media feeds are increasingly filled with data from public opinion polls. How do pollsters know which candidate is ahead in what swing state or with which key demographic group? Or what issues are most important to as many as 264 million eligible voters across a vast country?

In other words: How do pollsters do what they do?