In a major blow to the Congress ahead of Assembly elections in Himachal Pradesh,former Chief Minister Virbhadra Singh on Thursday resigned from the post of chairman of the partys campaign committee. Sources said Singh conveyed to AICC general secretary Birender Singh that he would not be attending Fridays campaign strategy meeting in Shimla. Singh,who resigned from the Union Cabinet after charges were framed against him in a corruption case,was made the chairman of the Congress campaign committee for Himachal Pradesh on July 16.