Politicians make good liars because they manage to convince themselves they are telling the truth, a study has revealed.
And this has also made it easier to hoodwink the public because the best liars are the ones who do not realise they are lying, said the study.
From Watergate to weapons of mass destruction (WMD), world leaders have been guilty of untruths whether it is blatant lies or honest mistakes, it claims.
But they may have fooled themselves into believing, for instance, that Iraq had WMD because it is what they wanted to believe, said political professor Dr Anna Galeotti.
Other examples include President Bill Clinton denying his affair with Monica Lewinsky and Richard Nixon claiming his innocence over the Watergate scandal that brought him down.
In each case, politicians may have been guilty of self-deception, Dr Galeotti, of the University of Eastern Piedmont, Italy, told the journal Political Studies.
Everyone has their own in-built lie detector but it is easier to spot someone who is lying deliberately than someone who is lying without, perhaps, realising it, she added.
Because of this, politicians not only lie convincingly, but are still convinced they are telling the truth even after they have proved to have lied, the report added.
And it may be more common in politics that many realised.
Dr Galeotti said: ‘Self-deception is a type of motivated irrationality – the art of believing something simply because it is desired to be true when evidence points to the very opposite.
‘The more convinced is a political leader, the more convincing he or she appears.
‘A charismatic leader is persuasive in proportion to his convictions and faith; a cynical, self-interested liar is more easily detected and can hardly become a charismatic leader.’
However, it may be that those who go on to become the most successful politicians are those who have most developed the ability to deceive themselves and to believe their own lies.
She said: ‘In order to sustain deception over time, one needs to be very alert, clever and consistent.
‘Some evolutionary psychologists maintain that humans have evolved sophisticated abilities of lie detector in order to counter the possibility of others’ deception; hence the most efficient way of deceiving others is to believe one’s lies.’