Dirty tricks are a natural part of politics. In fact, dirty tricks might be the most interesting part of politics. Without the backstabbing, lying, and character assassination, it would be nothing but subcommittee assignments and farm-subsidy debates.
Nobody recognizes the fundamental importance of dirty tricks more than campaign operatives. Hell, they live for that stuff. So crying foul when something bad happens to your guy - as opposed to something bad that you personally inflicted on the other guy - ...