Are polls getting less reliable? Some say so. Our changing technology, including social media and the 24-hour news cycle, can have an effect on opinions and behavior. People who hear that a candidate already has a good lead might change their opinion or not show up to vote. On the other hand, some estimates of the error rates of polls suggest that they are somewhat stable as pollsters change their methods to adapt to society's dictates.
Or are polls still pretty accurate, taking the pulse of the people? Some say so. If the difference between opinions is huge, then a poll can certainly pick that up. However, if opinions are just a few points apart, polls may not be able to show those differences accurately.