There's at least one short where this is fairly explicit - a politician is rumoured to be a robot, and nobody can prove it either way by his behaviour since the

There's at least one short where this is fairly explicit - a politician is rumoured to be a robot, and nobody can prove it either way by his behaviour since the actions of a very moral man are indistinguishable from those of a robot. Oh, and there's a similar theme to the R. Daneel Olivaw/Foundation mashup stories. (ChatGPT says it's "Evidence", 1946, so fairly early).