Make sure their ideas have been listened to carefully. If it seems that the rest of the group has considered their idea but there is still disagreement, ask if the one or two feel strongly enough to block Consensus. They may stand aside if they feel that the group has acknowledged their ideas. Sometimes people are willing to stand aside if special considerations can be made such as:
A) They don't have to do the work on a given task.
B) If their dissenting ideas are recorded.
C) If it is stipulated that the decision does not set precedent and therefore cannot be used as basis for future decisions.
D) A trial period set for testing the decision and its implementation (this would include a time for evaluation and re-negotiation if necessary).
Sources: Building Social Change Communities
Contributors: Susanne Terry, The Training/Action Affinity Group of Movement for a New Society
Recommended Books: Building Social Change Communities
If not then leave us a suggestion on how it can be improved