In Macbeth, which modern methods might Macbeth rely on if he were a leader today?
Consider the methods present-day politicians use to gauge public response to their actions and to shape their policies.
The primary method today's politicians use to determine public sentiment is taking a public opinion poll. If Macbeth had taken such a poll before murdering King Duncan, he would have found that Duncan was well loved and his assassination would be roundly condemned. However, Macbeth didn't need to take a poll to understand this. He knew quite well that murdering Duncan was an especially abominble act because Duncan was a good man and a just monarch. Macbeth knew that the grief over Duncan's death would be so great that "tears shall drown the wind."
A poll of the people after Macbeth gained power would have made clear early on what becomes increasingly clear to Macbeth as the play continues: The people of Scotland despise him. By the end of Macbeth's reign, before he is overthrown, the only Scots who fight for him are those soldiers who are forced to do so. Scotland suffers under Macbeth.
Had he been made aware of this earlier, Macbeth might have altered his policies, perhaps. In addition to focusing his power and attention on destroying his political enemies and maintaining the throne, he might have taken measures to win the people's approval. He could have shared some of his great wealth as Thane of Glamis, Thane of Cawdor, and King of Scotland to make the people's lives easier. In short, he could have at least tried to buy them off by making their daily lives easier.
He could have employed Lady Macbeth in a public relations campaign to improve his image. She certainly could perform as a convincing liar, one who could pretend very effectively to be a warm, sincere, and caring person. (Duncan was taken in, unfortunately.) If Lady Macbeth traveled from village to village, for instance, distributing food and blankets while sympathizing with the plight of the commoners, she might have won some hearts and minds. In some of Shakespeare's other plays, specifically in Julius Caesar, commoners are portrayed as being very easy to manipulate; perhaps Macbeth's disgruntled subjects could have been manipulated, as well.
Macbeth would have had one huge public relations problem, however, in trying to overcome his slaughtering Macduff's entire household. That would have been impossible to explain or rationalize.