Act I, scene ii, lines 56-80: Cassius is telling Brutus that everyone loves him and thinks he's great. Cassius is offering to show Brutus how favorably everyone looks upon him, if Brutus will listen to such a humble man as Cassius. Cassius is trying to get himself on Brutus' good side so Brutus will help with the conspiracy to kill Caesar. In fact, most of Cassius' speeches to Brutus in this scene are forms of manipulation.
Act I, scene ii, lines 304 to the end of the scene: this is Cassius not just speaking of munipulation but planning to lead Brutus into thinking that the commoners are concerned about Caesar as well. Cassius is going to write a variety of letters and make them look like they have come from other citizen in order to persuade Brutus to join the conspiracy.
Act II, scene ii, lines 93-104: Decius is manipulating Caesar to come to the Senate today by telling him he will be mocked if he doesn't, and that he will be offered the crown and the Senate may change its mind if Caesar doesn't come today.
Lastly, both Antony's and Brutus' speechs in Act III, scene ii are examples of each man trying to manipulate the crowd into believing each man is in the right.
In a scene that has been alluded to as "the seduction scene," Cassius seeks to convince Brutus of the faults of Julius Caesar in Act I, Scene 2. In this scene it becomes apparent that Cassius has a talent for manipulating others and controlling the direction of a conversation.
When he first greets Brutus, Cassius expresses worry that Brutus no longer wishes to be his friend:
I have not from your eyes that gentleness
And show of love as I was wont to have. (1.2.34-35)
These words move Brutus to insist that what Cassius says is not true; he is simply "at war" with himself. Cassius then flatters Brutus by telling him that many Romans respect him and speak of him when they complain of the tyranny of Caesar. Further, when they hear the flourish of trumpets and a shout arises, Cassius asks what the shouting is about and Brutus comments, "I do fear the people choose Caesar for their king" (1.2.80). The clever Cassius manipulates this comment by saying that if this possibility displeases Brutus, he must prevent it. Thus, Cassius makes his idea of preventing Caesar from gaining power seem like Brutus's own:
Ay, do you fear it?
Then must I think you would not have it so. (1.2.81-82)
Brutus then asks Cassius why he keeps him so long, adding that if Cassius's purpose is to speak of honor and the welfare of Rome, he will talk with him. Of course, this is exactly what Cassius has hoped for because now he has the opportunity to talk with Brutus about what he really wants. Therefore, when Brutus declares that he will talk of honor, Cassius affirms that it is, indeed, honor that is "the subject of my story" (1.2.94).
From this starting point, Cassius begins his persuasive argument. He questions why he should live in awe of Caesar when he, as well as Brutus, can both "Endure the winter's cold as well as he [Caesar]" (1.2.101). In other words, Caesar is but a man, just as they are. In order to prove that Caesar is no god, Cassius then tells Brutus how Caesar was once drowning and he had to save him. Further, Cassius alludes to another incident in which Caesar demonstrated that he is far from being a god, or able to be a single leader of Rome. He tells Brutus of a time that Caesar fell down and had what was probably an epileptic fit. Yet, adds Cassius:
A man of such a feeble temper should
So get the start of the majestic world
And bear the palm alone. (1.2.131-133)
Here Cassius tries to generate doubt in Brutus's mind about Caesar's strength and greatness. Stirring Brutus further, Cassius alludes to a brave ancestor of Brutus, Lucius Junius Brutus, who helped to expel the last King of Rome and help found the Republic in 509 B.C. Cassius reminds Brutus:
There was a Brutus once that would have brooked
Th'eternal devil to keep his state in Rome
As easily as a king. (1.2.186-188)
In Act I, Scene 2, Cassius manipulates Brutus by utilizing concepts that will surely move him. These concepts are the traditions of Rome, the image of Rome generated by its rulers, and the honor of the family of Brutus. Cassius ends his speech by cleverly diminishing himself. He says that he is glad that his
...weak words have struck but thus much show
Of fire from Brutus. (1.2.177-178)
Actually, Cassius is proud that he has moved Brutus to his way of thinking, which is to undermine Caesar.