2. A system, comprising: one or more processors; one or more computer-storage media; and executable instructions stored on the one or more computer-storage media and executable by the one or more processors to receive a search query and generate an optimal list of search results in response, comprising: (1) a candidate generator that determines one or more candidate search queries, each comprising variant terms corresponding to search terms of the search query, (2) a probability generator to determine probabilities that including results stemming from searches of the one or more candidate search queries in the optimal list of search results will result in a user interaction with corresponding online resources, wherein the probabilities determined by the probability generator are based on interaction scores and candidate scores for the one or more candidate search queries, wherein the interaction scores are based on user interactions with at least one of the results stemming from the one or more candidate search queries, and wherein the candidate scores correspond to probabilities that the one or more candidate search queries are effective replacements for the search query, and (3) a blending module to determine the search results for the optimal list of search results based on the probabilities determined by the probability generator.
2. A system, comprising: one or more processors; one or more computer-storage media; and executable instructions stored on the one or more computer-storage media and executable by the one or more processors to receive a search query and generate an optimal list of search results in response, comprising: (1) a candidate generator that determines one or more candidate search queries, each comprising variant terms corresponding to search terms of the search query, (2) a probability generator to determine probabilities that including results stemming from searches of the one or more candidate search queries in the optimal list of search results will result in a user interaction with corresponding online resources, wherein the probabilities determined by the probability generator are based on interaction scores and candidate scores for the one or more candidate search queries, wherein the interaction scores are based on user interactions with at least one of the results stemming from the one or more candidate search queries, and wherein the candidate scores correspond to probabilities that the one or more candidate search queries are effective replacements for the search query, and (3) a blending module to determine the search results for the optimal list of search results based on the probabilities determined by the probability generator. 11. The system of claim 2 , further comprising at least one member of a group comprising: an error module to correct any misspellings in the search query; and a language module to generate the variant terms.