Sponsored search results re-ranking based on linking associations

A computer-implemented system and methods of re-ranking sponsored search results by a search engine in response to a search query include: retrieving one or more organic search results and a plurality of sponsored search results ("search results"), along with their respective rankings, associated with a search query; determining a degree of association between each sponsored search result and the other search results through analyzing web links between the search results and other web documents to or from which the search results are at least indirectly linked; calculating a clustering score for each sponsored search result based on their respective degrees of linking association; generating a new ranking score for each sponsored search result based on their respective clustering scores and rankings; and re-ranking, and storing in memory, the plurality of sponsored search results based on the new ranking scores of each respective sponsored search result.