The polls are only trying to make it close so more people will come out and vote.
If they say the RATS are so far ahead, there will be a bigger GOTV movement by the Republicans while the RATS will kick back as they always do and hope the ballot stuffing carries the day.
Then when the Republicans win big time they call it a suprise and a moral victory. Keeping it close forces the RATS to GOTV.
Frankly, as long as the economy and the WOT are the Republicans talking points, they will win easily.