The Zimbardo Prison Experiment in 1971 suggested that those placed in roles of power tended to be corruptible and had power go to their heads.
http://en.wikipedia.org/wiki/Stanford_prison_experimentWhile this experiment has been repeated, many people don't want to believe that human nature is that corruptible or succeptible to the temptations of power.
"According to our research, power and influence can cause a severe disconnect between public judgment and private behavior, and as a result, the powerful are stricter in their judgment of others while being more lenient toward their own actions," he continued.
To simulate an experience of power, the researchers assigned roles of high-power and low-power positions to a group of study participants. Some were assigned the role of prime minister and others civil servant. The participants were then presented with moral dilemmas related to breaking traffic rules, declaring taxes, and returning a stolen bike.
Through a series of five experiments, the researchers examined the impact of power on moral hypocrisy. For example, in one experiment the "powerful" participants condemned the cheating of others while cheating more themselves. High-power participants also tended to condemn over-reporting of travel expenses. But, when given a chance to cheat on a dice game to win lottery tickets (played alone in the privacy of a cubicle), the powerful people reported winning a higher amount of lottery tickets than did low-power participants.
Three additional experiments further examined the degree to which powerful people accept their own moral transgressions versus those committed by others. In all cases, those assigned to high-power roles showed significant moral hypocrisy by more strictly judging others for speeding, dodging taxes and keeping a stolen bike, while finding it more acceptable to engage in these behaviors themselves.
Why Powerful People -- Many of Whom Take a Moral High Ground -- Don't Practice What They Preach