Data Loader throwing an error when trying to delete contacts

I am trying to delete contacts but am getting this error "UNABLE_TO_LOCK_ROW:unable to obtain exclusive access to this record or 1 records: 7013x000002XAKcAAO". The ID specified in the error is for a campaign that is no longer active.  Campaigns is not listed as a record in the list of "You can't delete contacts that have these records associated with them" from the 'Considerations for Deleting Contacts' help documentation. See below for that list 

• You can’t delete contacts that have these records associated with them.
  • Assets (with cases)
  • Cases
  • Contracts
  • Partner user
  • Service contracts
  • Active Self-Service users
  • Active Customer Portal users

Any ideas on how I can delete these contacts?