Source : Webster's Revised Unabridged Dictionary (1913)

Partisanship \Par"ti*san*ship\, n.
   The state of being a partisan, or adherent to a party;
   feelings or conduct appropriate to a partisan.

Source : WordNet®

partisanship
     n : an inclination to favor one group or view or opinion over
         alternatives [syn: {partiality}] [ant: {impartiality}]