Paul S. Reinsch was born June 10, 1869, at Milwaukee, Wisconsin. He received his higher education at the University of Wisconsin, where he was awarded the B.A. degree in 1892, the L.L.B. in 1894, and the Ph.D. in 1898. He became a full professor of political science at the University of Wisconsin in 1901, and remained in this position until 1913.
Reinsch was one of the organizers of the American Political Science Association, serving as second vice-president in 1904, and becoming president in 1920. He was one of the first educators to offer courses in world politics. In 1911 and 1912, he served as Roosevelt exchange professor at the universities of Berlin and Leipzig.
Reinsch was introduced into the world of practical diplomacy by serving on the United States delegations to the third Pan American Conference at Rio de Janeiro in 1906, the first Pan-American Scientific Conference at Santiago, Chile, in 1909, and the fourth Pan-American Conference at Buenos Aires in 1910. This experience, in addition to his reputation as a student of Far Eastern affairs, led to his appointment as Minister to China by President Wilson on August 13, 1913.
While Minister, Reinsch encouraged educational, industrial, and commercial development in China. He always remained sympathetic to the democratic movement, despite civil war, political intrigues, and two attempts to restore the Empire. His greatest fault as a diplomat was an inclination to “make Policy”-- that is, act without concrete instructions from Washington. The most serious instance of this was his promise to China that, if the Chinese would enter World War I against the Central Powers, the United States would support China's claim to sovereignty in Shantung Province. When, because of circumstances of which Reinsch had no knowledge, President Wilson allowed Japanese sovereignty over Shantung to be written into the treaty of peace, Reinsch resigned his position as Minister.
After his resignation in August 1919, he accepted an appointment as legal counselor to China. In this capacity, he represented China at the Washington Conference, and continued to lecture and write until his death on the evils of secret diplomacy and the value of better Sino-American relations.
In 1920, after his friend Joseph E. Davies persuaded him to run for the office, Reinsch won the Democratic Party nomination for Senator from Wisconsin. His campaign was not very actively pursued, however, and he was defeated in the election by Irvin Lenroot, the Republican candidate. Reinsch continued to work for China, and was in Shanghai, working on fiscal reform for the Chinese government, when he died on January 24, 1923.