As others have said, there are numerous ways that these polls can be manipulated to achieve the result those paying for the poll may intend.
However, I never pay attention to any national poll that says "Americans are split 53%/47% for Candidate X over Candidate Y".
We elect our presidents through the Electoral College. Gore's claim that he won the national popular vote, while true (and perhaps interesting) is absolutely irrelevant. You might as well compare how many people drove domestic cars to how many drove imports to the polls. It might tell you something about voters, but it has nothing to do with how we elect presidents.
Now show me a story about how each state is polling, and I'll pay attention. These, however, are very few and far between. These stories require actual legwork on the part of the reporters; They require Americans to understand that we're not voting for Senior Class President here; and they may not convey the agendas of the media.