Additional to this central role going to Mr. McCain, the part of Cassius will be undertaken by Senator Graham, according to breaking news.
Caesar himself will be performed by Alex Baldwin, renowned for his satirical reprise of Mr. Trump on Saturday Night Live.
The theme of the play is timeless, on the nature of power and a vain leader, with a fickle public, and plotters eager to do something.
Mr. Trump is reported eager to attend, and may tweet during the performance.
Lady Gaga has declined the role of Calphurnia, whereas the part of Portia is under deep consideration at this time by Beyonce.
Act I, scene 2 has recently been the focus of rehearsal with last night's session interrupted and started over due to Senator Graham's whispering to Mr. McCain, "Hell, this is more fun than impeachment!"
Unfortunately, this comment was caught by highly sensitive microphones, and Director Robert Kagan immediately halted proceedings.
His wife, Assistant Director Victoria Nuland, rushed onto the stage to scold the senators, saying, "This is not senate chambers! This is serious!"
Both senators bowed and appeared humbled.
Mr. Baldwin has been reported spending a lot of time getting the "Et tu, Brute" moment just right, in a combined tone of bewilderment and disappointed love.
He has said he is having trouble with the "love" part of the tone because he wants to over-write this moment to "I always knew you were a back-stabbing motherf**ker."
Purity, however, is essential to rendering Mr. Shakespeare's work accurately, especially given how appropriate the story of Julius Caesar is to our own time.
As Cassius, Senator Graham is reported having some difficulty remembering all his lines, but is particularly fond of this comment on Caesar, spoken to Brutus (Senator McCain):
Why, man, he doth bestride the narrow world
Like a Colossus, and we petty men
Walk under his huge legs and peep about
To find ourselves dishonorable graves.
In an earlier part of the play, Mr. McCain and the Director are reported in some contention when Brutus says, "Chew upon this: Brutus had rather be a villager than to repute himself a son of Rome under these hard conditions . . ."
Mr. McCain has argued he should be able to insert "a humble senator from Arizona" for "villager" and "this Great Nation" instead of "Rome."
At another point Mr. McCain, in the role of Brutus, stated of Caesar: "He is fat and scant of breath," which immediately brought the Director running onto the stage.
"Wrong play!" he shouted. "This is not Hamlet!"
But Mr. McCain requested the line be inserted anyway.
Mr. Kagan has mused the company may do Hamlet next--if Mr. Trump will consider taking on the role.