Dice Milton Friedman en Free to Choose

Hablando de cómo el “clima de opinión” influencia el tipo de políticas que se ponen en práctica en un momento determinado:

In our opinion the Socialist party was the most influential political party in the United States in the first decades of the twentieth century. Because it had no hope of electoral success on a national level (it did elect a few local officials, notably in Milwaukee, Wisconsin), it could afford to be a party of principle.

The Democrats and Republicans could not. They had to be parties of expediency and compromise, in order to hold together widely disparate factions and interests. They had to avoid "extremism," keep to the middle ground. They were not exactly Tweedledum and Tweedledee—but close to it. Nonetheless, in the course of time both major parties adopted the position of the Socialist party.

The Socialist party never received more than 6 percent of the popular vote for President (in 1912 for Eugene Debs). It got less than 1 percent in 1928 and only 2 percent in 1932 (for Norman Thomas). Yet almost every economic plank in its 1928 presidential platform has by now been enacted into law.