corrupt |kəˈrʌpt| adjective1 having or showing a willingness to act dishonestly in return for money or personal gain
Most politicians, even in democratic societies, are corrupt. It is part of the job description to misrepresent intentions and hide actions in order to maintain power and/or implement an agenda. Voters do not respond to honesty if the honesty does not fit their preferred narrative. Speaking truth and facts also exposes them to weaknesses that will be exploited by rivals. So they hide, lie, and spin with differences measured only in degree.
The system, the social contract, demands corruption because we accept nothing else.