Did the Politoed have the Drizzle ability (was it raining when you were battling)? Was it EV trained in Special Attack? Was it holding Choice Specs? If any or all of the above things are correct it's possible that you were beaten fair and square.
I don't think you EV trained your Pokemon to withstand special moves (Conkeldurr or Magnezone especially) or outspeed Politoed (Excadrill).