Why politicians lie?

• Politicians lie, or don’t tell the whole truth, because they have to. It is a global phenomenon.
• We all know that politicians tell lies. We expect them to stop once they hold office. No longer. In campaigns, and in office, politicians and their aides or supporters deliberately lie about matters of importance. 
• At one time, citizens could count on their officials and candidates to either tell the truth or say nothing. Not any more. 
• In order to brush away the delusion and confusion that hides the truth from us, we need the truth, because only an accurate description of the facts will allow us to make sound, sane, and sensible decisions.
• It is amazing how often politicians lie with ease and then, their unwillingness to admit that they lied. Politicians’ words were distorted, misrepresented, twisted, exaggerated, or taken out of context. They overstated, understated, or misstated. But, of course, politicians never lie, at least that’s what they say.
• Politicians have a personality that allows them to be evasive, to live with lies and keep a straight face. Not all people can do that. That is why many people are not willing to serve in a political role. They detest the process they will have to follow, a process an inevitable byproduct of the political system we chose to have.
• Politicians know their followers will believe them, even in the face of irrefutable evidence to the contrary. Politicians and their adherents live in an echo chamber in which everyone watches the same news channel, listens to the same talk radio, reads the same newspapers and web sites, and hangs out with the same like-minded people. There exists an impermeable membrane that prevents conflicting information from entering.
• In elections, what was fascinating was that the more a candidate lied, the higher they went in the polls. The person who lied the most won. With no real arbiters of the truth, there were no penalties for lying.
• The public ignorance makes lying an effective political strategy. Politicians lie because the cost/benefit ratio for lying is in their favor. Politicians run this calculation when they create or shift a damaging narrative, attack an opponent, or respond to indefensible claims against them. Most politicians know when they are lying. So, politicians lie when they believe that dishonesty is the best policy for getting elected.
• People don’t want to hear the truth. Truth hurts and no one wants to hear things that threaten their existence, their beliefs, or that will make them uncomfortable. It is decidedly better for politicians to tell people what makes them feel comfortable. Why should politicians be the purveyors of bad news when they can tell fairy tales with happy endings and come out the victor.
• The more democratic the system, the more lying there will be. In a democracy a leader has to make difficult maneuvers in a politically competitive environment. That is what democracy is about.
• CEOs of very large companies, leaders of major conglomerates and of countries exhibit very similar leadership styles. They are evasive, play their cards very close to the vest and do not share information if they can help it. They use big words to obscure their real intentions. They often lie, skirt the truth, too.
• The higher you ascend up the hierarchy, the more political the environment becomes. There is a struggle between the interests. As a leader you have to maneuver between all these pressure groups and powerful individuals, and survive the maneuvering.
• Being truthful is like a military leader making his battle plans known to the enemy during a war. Up there in the organizational hierarchy, whether of a country or a corporation, it is a war.
• Lying by political leaders is what we expect from totalitarians. Free societies require truth and honesty.
• The problem is inherent in objective journalism. In objective journalism, with an unfortunate amount of truth in it, there is no objective reality, there are only sources and they are rated by their credibility, and credibility is an attribute of status.
• There are only competing sources and competing spin and the journalists either don't know it or don't know what to do about it, journalists no longer own reality.
• People have not lost trust in journalism because they're liberal or biased or opinionated, but because they are not aggressive enough.

I offered my opponents a deal: if they stop telling lies about me, 
I will stop telling the truth about them  ... Adlai Stevenson, 
US Presidential Democratic candidate said in his 1952 campaign speech

While lies are impressive, truth is unpalatable. Lies travel much faster than truth. Probably that might be reason for people resorting to lies very often more so by politicians, corporate CEO's, journalists and so on. Public memory is short and also there are no penalties for lying. In the recent Gujarat elections Rahul Gandhi spoke truths but could impress less where as PM Modi resorted to wholesale lying which reverberated across media and the country and he ended up winning the election which otherwise would have been lost. Nehru was the first and the last Prime Minister who spoke truths fearlessly not bothering for consequences.