If you take a poll specifically for a set of people and everyone participates in it than yes that would be accurate. But to take a poll of a group of people than say they represent the entire state, than no they no longer count. As long as the poll is done right and actually states who took it and what it applies to though it can be accurate.
Having taken some phone and some email surveys, I can say that they are not very accurate for several reasons. One is the demographic of who is available to take them. Another is the way the questions are asked. You can tell if you are intelligent when the questions do not give the person the chance to say what they might really want to say and are skewed.