The Mugwumps were Republican political activists in the United States who were intensely opposed to political corruption. They were never formally organized. Typically, they switched parties from the Republican Party by supporting Democratic candidate Grover Cleveland in the presidential election of 1884. They switched because they rejected the long history of corruption associated with Republican candidate James G. Blaine. In a close election, the Mugwumps claimed they made the difference in New York State and swung the election to Cleveland. The jocular word "mugwump", noted as early as 1832, is from Algonquian mugquomp, "important person, kingpin", implying that Mugwumps were "sanctimonious" or "holier-than-thou" in holding themselves aloof from party politics.

The Republican Party, also known as the GOP, is one of the two major political parties in the United States. It is the second-oldest extant political party in the United States after its main political rival, the Democratic Party.