After hearing about an incredibly contentious tenure case at my alma mater and several other contentious ones, I'm curious to hear how such issues come to be. Some issues that seem to be at play: personal animosity between faculty, dispute about the merits of the candidate's research, scarcity of resources and discrimination based on gender, sexuality, religion and other aspects of identity. Some of these are legitimate, while others are clearly not. For those curious as to how nasty things can get, I recommend reading here. The account is both appalling and fascinating.
Do faculty see these issues coming? Are there tell-tale signs they might miss? One person I talked to was quite surprised both by the animosity one fellow faculty member had towards him and by the degree of influence this brought to bare on his tenure case.
Once such issues have been identified, how can the candidate defend against them? At what point should he/she be prepared to defend against them? From the other side, what processes exist to prevent such biases from influencing the process? Are they functional, and to what degree? Are there better practices that could be implemented to avoid such discontent?