Political ads? Never seen one...

Apparently there has been talks of political ads bashing the other candidate and promoting the candidate that runs the ad... aparently there have also been fake ones which dub voices to make it look like someone said something that they didn't. They must not do a very good job because I have never seen one of these ads in my life, neither have almost every one of my friends. Do they only play these ads on shitty channels like the public school channel or TNT, TCM, or that other one where they redecorate houses and shit? Please explain.