Nader-effect Definition

noun

(politics) The later term to describe the effect a candidate for the corresponding political office (especially the office of President of the United States) can have on a close political election, in which their candidacy results in the election being won by a candidate dissimilar to them, rather than a candidate similar to them.

Wiktionary

Origin of Nader-effect

Named after Ralph Nader, whose candidacy for President of the United States in the year 2000 was contended to have "spoiled" the election for Al Gore, by taking away enough votes for Gore in Florida and many other states to allow George W. Bush to win.

From Wiktionary