Brewer's: Mugwump Press
(The). Those newspapers which are not organs of any special political party, but being “neither hot nor cold,” are disliked by all party men.
“The Mugwump Press, whose function it is to enlighten the feeble minded ...” —The New York Tribune, 1892.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894