How does the political situation change in "Hamlet" Act 4?

There are several changes in the political situation in Act IV. The first change begins with the death of Polonius. This action forces the return of Laertes to Denmark. Laertes is furious over the death of his father and the way the funeral was handled. As he stands outside Elsinore, he gathers a mob which yells, "Laertes will be king." Claudius, who is stuggling to keep his throne, now has another rival for it. He deftly handles Laertes and convinces him that he was not responsible for Polonius' death. While Laertes and Claudius are speaking, Hamlet, who has been sent to England, supposedly to die, announces his return to Denmark. This is another threat to Claudius who turns to Laertes and together they plot to kill Hamlet. One significant scene that the audience may miss is the scene where Hamlet encounters the Captain of Fortinbras' army. Claudius promised Fortinbras safe passage through Denmark while Fortinbras is on his way to Poland. This will also set up another political change later in the play.