Most people who are successful in leadership or management positions need to have the ability to influence people or at least get them to do things (so a typical middle manager may not be particularly charming or charismatic, but his or her authority within the organization causes subordinates to obey). Higher-up politicians and world leaders do, though, tend to need a little more charisma to be successful or at least the willingness to hire a public-relations firm to manufacture the right image. Manipulation, though, is not equivalent to positive influence, and this is something of a moral judgment. Manipulators count on keeping their victims in the dark about their true intentions and tend to exploit a person's weaknesses rather than trying to build them up in a positive way. A manipulator may prey on someone's loneliness, the victim's own greed, or even the victim's generosity (becomes a "weakness" when the giver is deceived). The manipulator is interested in their own gain and doesn't care about the impact on others. To some extent, though, intrigue is normal in politics and diplomacy and always has been: Opposition parties, other countries, and even the body public can be part ally and part enemy, and relationships are managed sometimes through deceit (as WikiLeaks has shown us). Spies, public-relations specialists, and campaign strategists, though, would tend to be the ones to specialize in this duplicity. Unlike Machiavellians, psychopaths have a compulsion to lie even where it doesn't make sense, though; they do it for the thrill or the feeling of power it gives them. Psychopaths will lie and play tricks just for fun, purposelessly; I don't think you'll find this sort of pathological lying in the average politician, who is more constrained and image conscious.
Relating to that purposeless lying, psychopaths tend to be highly impulsive and reckless. When they get angry or frustrated, they will lash out violently or throw a temper tantrum. You generally don't see this from world leaders (in public), but sometimes you hear that powerful politicians and CEOs have tempers behind closed doors. Relating to the impulsivity is a general and extreme fearlessness and sensation seeking. Psychopaths crave a very high level of physical sensation: extreme sports, drug use, sexual promiscuity, wild parties, risk taking, etc. Sometimes you also hear about powerful people living wild lives just below the public radar (and often not even below the radar for celebrities).
The most defining characteristic, though, of the psychopath is the complete lack of social emotions like empathy and guilt.