running mate

from WordNet (r) 3.0 (2006)

running mate
    n 1: a nominee for the lesser of two closely related political
         offices

from Moby Thesaurus II by Grady Ward, 1.0

21 Moby Thesaurus words for "running mate":
      also-ran, aspirant, baby kisser, buddy, candidate, chum, comate,
      companion, comrade, crony, dark horse, defeated candidate, dud,
      favorite son, hopeful, lame duck, office seeker, pal,
      political hopeful, presidential timber, stalking-horse