As used in the U.S., the term is often similar to power politics, while in Germany, Realpolitik is used to describe modest (realistic) politics in opposition to overzealous (unrealistic) politics, though it is associated with the nationalism of the 19th century. The most famous German advocate of “Realpolitik” was Otto von Bismarck, the First Chancellor (1862-1870) to Wilhelm I of the Kingdom of Prussia. Bismarck used Realpolitik to achieve Prussian dominance in Germany, as he manipulated political issues such as Schleswig-Holstein and the Hohenzollern candidature to antagonize other countries, possibly with the intention of war. Characteristic of Bismarck's political action was an almost Machiavellian policy; he acted with little regard to ethics, morals or legalities. Prussia's seemingly illogical move of not demanding territory from a defeated Austria, a move that later led to the unification of Germany, is one of the often-cited examples of Realpolitik.
Similarly, in the German Green Party, people willing to compromise are referred to as Realos (realists), and opponents as Fundis (fundamentalists or ideologues).
Realpolitik is distinct from ideological politics in that it is not dictated by a fixed set of rules, but instead tends to be goal-oriented, limited only by practical exigencies. Since realpolitik is ordered toward the most practical means of securing national interests, it can often entail compromising on ideological principles. For example, the U.S. under the Nixon and Reagan administrations often supported authoritarian regimes that were human rights violators, in order to, theoretically, secure the greater national interest of regional stability. Detractors would characterize this attitude as amoral, while supporters would contend that they are merely operating within limits defined by practical reality.
Most recently, former ambassador Dennis Ross advocated this approach to foreign policy in his 2007 book Statecraft: And how to Restore America's Standing in the World.
For the purposes of contrast, and speaking in ideal types, political ideologues would tend to favor principle over other considerations. Such individuals or groups can reject compromises which they see as the abandonment of their ideals, and so may sacrifice political gain in favor of adhering to principles they believe to be constitutive of long term goals.