DOPS: Couldn't an attacker that controls 51% of a DPOS network mine blocks in disguise and this way double spend coins when his hidden chain has caught up?
Contra argument: When 51% of the delegates mine a hidden chain they can't mine the currently longest chain. This would lead to them being "unvoted" (based choice of words for approval voting i can think of).
POW: If the Ghash mining pool operator begins to mine a hidden chain he couldn't mine for profit in the mean time and all miners with Ghash would jump off the Ghash pool.
Is mining a hidden chain the only way to double spend?