Vidur Niti, also popularly known as the wisdom of Mahatma Vidura is part of Mahabharat, Udyog Parva. It is a conversation between King Dhritarastra and Vidura. It elaborates on topics as varied as forgiveness, desire, anger, misuse of tongue to moral terpitude, sin, virtue, virtuosness, slander and reproaches. It explains how, what, when and why of politics that would help Dhritarastra choose righteous path of action.
This recently revised PDF includes
1) Sanskrit text of Vidur Niti from Mahabharat, Udyog Parva, Chapter 33 to 41.
2) English translation from MAHABHARATA by Kisari Mohan Ganguly.
3) Excerpts in Gujarati from MAHABHARAT NA MOTI by Shri Yogeshwarji.