It is true that a commitment to being ethical is important for good leadership. When you are a leader, people look up to you and consider you to be their role model. Then it is only natural that you should behave in a moral way and do what is right for your people and your country. If you are a corrupt leader, people are likely to rebel and oust you from your position, but if you are a righteous leader, most of the people are going to love you and trust you.
