The people most likely to watch a televised debate between political candidates are the most committed members of the electorate and thus the most likely to have already made up their minds about whom to support  Furthermore, following a debate, uncommitted viewers are generally undecided about who won the debate
Hence, winning a televised debate does little to bolster one' s chances of winning an election
the voting behavior of people who do not watch a televised debate is influenced by reports about the debate