The free market vs. politics

The free market always maximizes ex ante social utility as well. In political action, on the contrary, there is no such mechanism; indeed, the political process inherently tends to delay and thwart the realization of any expected gains.

... says Rothbard in Power and Market (chapter 2). This is why the libertarian is more interested in advocating the free market, than he is in advocating any particular political system (such as democracy). It is through increased economic freedom that people become better off, not through any one type of political system or another.