I believe this question is wrong. And I have a strong reason to believe that. First of all its stereotyping. Not necessarily all politicians lie.. there are good people who joined the politics for doing so good. But the reason is there are so many difficulties that they have to get through before they can make their promises a reality. Then again not everyone has the same mindset. What I am saying is that not every politician is a liar. Just like not every policeman or government officials are corrupt.
Although if you there is anything we can do about the situation is to appriciate the good decision and deed if any of the politicians managed to get it done.. I feel sad if I ever put myself in their shoes most of the time they are labelled bad guys even before they get to prove their worth. Working under constant lynching is really tough, no wonder may give up and just stop resisting..
And if you look at the question other way.. aren't we all liar.. if lying is not keeping your promises.
Regards
@inuke