Internal polls might mean squat to you, but not to those who pay for them. They rely on their accuracy and the politicians with flush war chests buy the best, the ones with the top track records for proven accuracy.
Give me a break.
If you have to commission an internal poll, that means you're not confident in your political standing to begin with. It's the equivalent of paying someone to give you a good psychic reading.
Hahaha tell that to Cantor. His polls showed him with a comfortable lead the day before the primary.