1. A computer readable storage device storing a program of instructions executable by a machine to perform a method of diffusing evidence among candidate answers during question answering, comprising: identifying, by a processor, a relationship between a first candidate answer and a second candidate answer, wherein the candidate answers are generated by a question-answering computer process for answering a question, the candidate answers have associated supporting evidence, and the candidate answers have associated confidence scores; determining whether to transfer the associated supporting evidence from the first candidate answer to the second candidate answer, or to transfer the associated supporting evidence from the second candidate answer to the first candidate answer, by analyzing how the question is posed and types of the first candidate answer and the second candidate answer; in response to determining to transfer the associated supporting evidence from the first candidate answer to the second candidate answer, transferring all or some of the evidence from the first candidate answer to the second candidate answer based on the identified relationship, and computing a new confidence score for the second candidate answer based on the transferred evidence and second candidate answer's existing evidence; in response to determining to transfer the associated supporting evidence from the second candidate answer to the first candidate answer, transferring all or some of the evidence from the second candidate answer to the first candidate answer based on the identified relationship, and computing a new confidence score for the first candidate answer based on the transferred evidence and first candidate answer's existing evidence.