There is a battle going on behind the scenes in the race between Barack Obama and John McCain. The winner of this conflict will probably decide who wins the presidency. In the blue corner, there is the "new vote" - those who are going to vote this year for the first time in the general election. These folks have been inspired by Obama's entrance on the national stage and are awaiting their chance to pull the lever. They will vote primarily for Barack Obama. In the red corner, there is the Bradley Effect, represented by white voters who say they will vote for
Obama because they fear being thought of as racist. Once they get into the voting booth, however, they'll vote for John McCain.
Polling companies have a very difficult time quantifying either of these competing factors. Their likely voter models rely on previous voting patterns, which can under-represent the new vote.
Yet, they depend on getting the true intent of the people they poll, thus leading to the Bradley Effect. How well polls reflect these factors will determine how accurate they are. If the actual size of the new vote out paces the Bradley Effect, Obama will perform better than the polls predict. But if the Bradley Effect is larger than the new vote, McCain will enjoy an unexpected boost on Election Day.
Say what you will about polls, the winner of the election very likely will be the one who benefits most from these two currents running below the surface. But because they are unmeasurable, at least until after the election, the outcome of their battle is one of the biggest question marks of this election.