Truth be told, all politicians lie to get elected. Some get away with telling lies more than others. The real reason why politicians lie is because the public doesn't want to hear the truth. The 2016 presidential election is an example of this.
According to published reports, Donald J. Trump’s record on truth and accuracy is astonishingly poor. So far, there have been a series of them fact-checked and more than 70 Trump statements and rated fully three-quarters of them as Mostly False, False or “Pants on Fire” (we reserve this last designation for a claim that is not only inaccurate but also ridiculous)
http://www.politifact.com/personalities/donald-trump/
The Trump supremacy http://www.politico.com/story/2016/02/donald-trump-south-carolina-gop-f…
The Top 10 Political Lies of the Year http://www.thefiscaltimes.com/2015/12/21/Top-10-Political-Lies-Year#.Vs…
The Biggest Presidential Scandals in History | InsideGov http://us-presidents.insidegov.com/stories/5289/biggest-presidential-sc… via @GraphiqHQ
Why people lie https://youtu.be/rIyfUrGNr4g via @YouTube
The Truth about Liars and Lies - Documentary Films https://youtu.be/Ku1zP4de3WE via @YouTube