In 5 of the last 9 years, the team that opened up the initial BCS poll at the #1 position finished at the top spot after the conference championship games. Only two of the nine teams finished outside the top 5, and none finished outside the top 10. In the table below, the losses column indicates the number of losses from the time the first BCS poll was released through the week of the conference championship games.
1st BCS Poll
The moral of the story is that teams that open up in the #1 spot are very hard to unseat unless they lose. In 2007, enough crazy shenanigans happened that allowed Ohio State to jump back to the #1 ranking despite a loss after the first BCS poll was released.