MOE is tied generally tied into the concept of confidence interval.
If you have a MOE of 2% that means that generally, if you were to preform the same measurement with the another randomly selected population of the same size, you would get the same result 98% of the time.
If you have a MOE of 2% that means that generally, if you were to preform the same measurement with the another randomly selected population of the same size, you would get the same result 98% of the time. Actually, a MOE of 2% means that the probability is high (usually 95%, a value rarely stated, but a standard one) that the true mean of the population is within 2% of the result you saw.
This of course assumes that the population is well defined and that each item in the sample (voter) has an equal likelihood of being chosen. Neither of these are true, so we put a degree of precision on these polls that simply are not justified.