"Power is poison. Its effect on Presidents had always been tragic"

Henry B. Adams' quote speaks to the idea that power can be a hazardous thing. It can have a corrupting influence on those who wield it, leading to awful repercussions. This is specifically real for Presidents, who have a great deal of power and impact. The power of the Presidency can be intoxicating, resulting in a sense of invincibility and a disregard for the effects of their actions. This can result in dreadful outcomes, both for the President and for the nation. The quote functions as an alerting to those in power to be mindful of the possible threats of their position and to use their power properly. It is a reminder that power can be a double-edged sword, which it must be handled with care.