Over ride of power key doesn't override but adds to the function

[flipside101]

I may be doing it wrong but when I use the code below (it calls a switch that toggels a Logitech harmony activity) the first press of the power button triggers the standard TV power on function, the second press triggers the activity on , third toggels it off.

keys: POWER: service: switch.toggle data: entity_id: switch.tv