I should note that the MOE used here is for polling. However, there is MOE in anything you measure. For instance, there are a dozen or so reference weights (kilograms) in the world. They are regularly measured, checked, rechecked and so on. There is error in every single measurement (weighing). While the reference weights weigh very very close to a kilogram, they do not weigh exactly one kilogram. And each time they are measured, there is an error in the measurement.