a Republican who refused to support the party nominee, James G. Blaine, in the presidential campaign of 1884.
2.
a person who is unable to make up his or her mind on an issue, esp. in politics; a person who is neutral on a controversial issue.
Origin: 1830–35, Americanism; artificial 19th-cent. revival of Massachusett (E sp.) mugquomp, syncopated form of muggumquomp war leader (equiv. to Proto-Algonquian *memekw- perh., swift + *-a⋅pe⋅w man)
1832, jocular for "great man, boss," Amer.Eng., from Algonquian (Natick) mugquomp "important person," used since 1884 of Republicans who refused to support James G. Blaine's presidential candidacy, hence "one who holds himself aloof from party politics."