I'm leaning toward the position that there is little or no difference between advocacy and lying. Has any other philosopher discussed this in detail?

Check out Tom Carson's book Lying and Deception (Notre Dame University Press). It's brilliant. I am not sure why you are leaning to equate lying and advocacy. Maybe you have in mind the idea that when persons advocate for a cause or person they might be tempted to do *anything* on behalf of the cause or person. I will admit (and hope that my college administration is not reading this) that my advocacy on behalf of some students has led me to "stretch the truth" a bit (or lie), but this is rare! Check out Carson's book. It is brilliant.

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