The incessant competitive struggle to get into office or to stay in it imparts to every consideration of politics and measures the bias so admirably expressed by the phrase “dealing in votes.” The fact that in a democracy government must attend primarily to the political values of a policy or a bill or an administrative act … is likely to distort all the pro’s and con’s. In particular, it forces upon the men at or near the helm a short-run view and makes it extremely difficult for them to serve such long-run interests of the nation as may require consistent work for far-off ends; foreign policy, for instance, is in danger of degenerating into domestic politics. And it makes it no less difficult to dose measures rationally. The dosing that a government decides on with an eye to its political chances is not necessarily the one that will produce the results most satisfactory to the nation.
In short, no miracle occurs to transform the same humanity that operates imperfectly within private markets into a god-like force when it operates in political spheres.
(Schumpeter is correctly regarded as having helped lay the ground work for the emergence of the public-choice scholarship that begin in the second half of the 20th century.)