What role does "character" play into the Heisman selection?

All the Cam Newton allegations got me thinking - at what point do off the field incidents take you out of Heisman contention?  Is character a stated requirement?

Clearly, off the field issues can matter at some point (see Reggie Bush).  Do the off the field issues have to be so serious that they destroy a person's eligibility to play in games to kill a person's Heisman chances/award?  I was trying to think of an instance where a clearly more talented player was passed over for the explicit reason of characted but can't think of anyone.

NOTE: this is not a thread to condemn Newton for the allegations against him; he is innocent until proven otherwise (other than laptop stealing).  I'm of the personal opinion that we should be very careful in who we select because these guys become the face of college football, role models for tons and tons of kids, etc.  But that's neither here nor there.