Anon21003- I don't know the answer to your question, but I did want to say that I think that presidential polls are often really wrong and sometimes it just has to do with other things than the Bradley effect.
While I understand the Bradley effect can skew polling data in favor of a certain candidate incorrectly this is not the only reason why that would happen. For example, in the Presidential election of President George W.Bush and Senator John Kerry the exit polling data showed that Kerry would beat President Bush by a 5% margin.
The results were the opposite and President Bush was reelected. I think the reason this problem occurred in the polling data was the possibility that Democratic voters were oversampled and that is why they showed that Kerry was going to win. While this situation did not have a Bradley effect it did have an inaccurate poll that happens all of the time.
With the next upcoming Presidential Race who knows if there will be a Bradley effect, but I have learned to take all polling data with a grain of salt.