When you look at individual polls and see them all over the map that doesn't mean that polling is inaccurate.
Let me give you an example. Say there are 10 people in a group. I want to conduct a poll on their opinion of abortion. I don't have the resources to poll all 10 people so I will only poll 5 of them. Now in this group, 7 people are PRO abortion and 3 people are ANTI abortion.
In my first poll, in which I poll 5 people, let's say I end up calling the 3 who are ANTI abortion and only 2 that are PRO abortion. From this sample it would appear that 60% of the people are ANTI abortion and 40% are PRO abortion. Doesn't make sense with what we know right?
Now, let's say I repeat this poll many many times over the course of months and years. Probability will eventually win out and the polls will reflect that indeed more people are PRO abortion than ANTI abortion. That's why I highly recommend you go to
www.fivethirtyeight.com. They have statistical models that help make sense of all this polling data.
Polling isn't an exact science by any means, but it CAN give you a good idea of where the race stands if there is enough data.