I say it was the mistress. The back seat is demeaning. I saw her on the tube tonight - she seemed like a bit of a bubblehead. I suspect she wanted the whole world to know about their “love” for each other.
Could be the mistress was sick of hiding and wanted him to choose...... but it could have been the ‘friend’ of the mistress who helped set up the rendevous and drove her there — maybe that guy decided that getting big bucks from the National Enquirer was better than being a gofer for the John Edwards mistress.