Iago is the master manipulator. His manipulations work because people trust him.
Shakespeare presents Iago as the kind of person who performs character assassination through insinuation. He drops a hint that something is wrong; then, when he is pressed, he protests he didn't mean to say anything or that he likes the person in question too much to want to say what he knows. Then, when he is pressed to tell, he lets the curious person drag a lie out of him, as if he is unwilling to betray anyone.
He does this with Othello , pretending that the last thing he wants he to do is to implicate Cassio as Desdemona's lover. Only when Othello insists does Iago tell the lie that, while dreaming, Cassio mistook Iago for Desdemona, flung his leg over Iago's thigh and kissed Iago on the mouth while murmuring that he wished Othello was dead. All of this is an utter fabrication, but...
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