In my campaigns, the Paladin is not a champion of a god (that's what Clerics are). I prefer the classic D&D Paladin that is a Lawful Good virtuous Warrior with magical abilities.
I'm very sure that the confusion of what a Paladin and a Cleric is, is apart of the anti-alignment campaign that I see going through forums. It's a shame how this has worked out. The idea of the D&D Paladin has to be purposely misinterpreted and changed to allow those that hate alignment continue their arguments. The source of the Paladin's powers come from his Lawfulness and Goodness, at least it is strongly implied, because well Alignment influences the material world of D&D and Paladins tapped into that. Yet, if there is no concept of Alignment, at least one that does not affect the material world of D&D, then what is the source of a Paladin's powers? Oh they must get them from a God, and that means that Paladins are Champions of Gods, and that means that each God can have a Paladin then. See the logic behind it? The classic Paladin stands in the way of those that want to eliminate Alignment, which is why those that don't like alignment don't like the classic Paladin.
Druids, like Paladins, are also not worshipers of a specific god, but are more of a mystery religion/secret society that passes their magical training down to their initiates as they move up their in ranks. This is how I interept the Classic Druid.
I see Paladins in much the same way as the Druid in that they both do not learn their magical abilities from a God but through their special knowledge and training that they pass down to their apprentices or squires. The Order of Paladins is in fact an Order of Paladins; a society of knightly monks with magical powers. If they stop being Lawful Good they stop having powers because well the forces of Law and Good are the true magical source.