FCC Chairman Ajit Pai's surprise announcement that he was proposing designating the Sinclair-Tribune merger for a hearing before an administrative law judge, citing possible violations of law, drew strong reaction from deal critics suddenly facing a victory they thought was a long shot. A source says Pai already has the votes to approve the designation, with only commissioner Michael O'Rielly yet to vote, but signaling he could support it. Such a hearing could take more than a year and in the past such designations have been deal-killers. It also virtually insures that a legal challenge to the UHF discount, a challenge whose decision could also undo the merger, will be decided before the FCC ultimately weighs in.