The Nature of Government

It's true that people who get into politics tend to drift more left wing in general. However, the reason for this is not at all positive.

People in government begin to see government as a tool with which to solve every problem, and naturally wish to expand the authority of government (i.e. their authority) to make this possible.
They forget or choose not to remember that they were not elected or selected to expand their own authority, merely to effectively manage the affairs and duties of their office.

It takes a very special kind of person to go to work every day with the spirit of making his job obsolete. The War on Poverty has lasted for 40 years now, with little to show for the trillions pumped into subsidizing hundreds of thousands of middle class civil servants, who have only helped to perpetuate poverty, despite their good intentions.

This is why government programs never shrink; they expand, even in the face of failure, for the only solution these people understand to any problem is... more government.