Colin, it is confusing for the general public because they get a simplistic number (48% to 46%! 52% to 41% ) jammed at them daily, but that number does not actually reflect who will end up in the whitehouse, rather a popular vote trend, which feeds into the electoral college. The electoral college is where the real magic occurs, and it is rarely talked about in detail with these polls - they just give "a number".
Because the vote gets broken up 50+ ways the effective error rate in any single state is very high (2000 people spread over 50 states, that is 40 people per state average, which is statistically too low of a sample to be respresentitive, especially in states like California, New York, and Florida). They would have to sample something like 1000 people in EACH of those states to get numbers that even begin to express the voter direction in each state, which would then give a much clearer picture of the overall electoral college (and therefore election) situation.
There is a site posted,
http://www.electoral-vote.com/pred/index.html - I don't agree with their methods, but this to me is a better indication of WHO will end up in the whitehouse.
The straight 49%-48% suggest that each american gets an even vote, and we know that just isn't true. Overvotes in one state do not diminish or take down over votes in another. So measuring it overall isn't a true indication of the outcome either (Ask Gore).
Alex