I would have thought that the only conceivable basis for judging who “won” last night’s presidential debate between Barack Obama and John McCain was which candidate converted the most undecided voters into supporters. On that basis it was no contest. Barack Obama overwhelmingly won. See here for a good analysis of how undecided voters' reacted to the debate.
But the tv network talking heads who provided instant analysis immediately following the debate must have had some other criteria. If you figure out what that was could you let me know?