estimate 71.6 million people watch final debate white house contenders hillary clinton donald trump tv wednesday audience first encounter third-largest total ever record data supply nielsen rat agency thursday cover people watch wednesday night debate four main u.s. broadcast network plus nine cable public television channel first clinton-trump face-off september attract total tv audience 84 million large history u.s. presidential debate last week second debate broadcast opposite popular sunday night football see 66.5 million wednesday audience rank third-highest u.s. presidential debate since nielsen start collect tv viewership figure encounter 1976 1980 debate democratic president jimmy carter republican challenger ronald reagan draw 80.6 million viewers nielsen data reflect watch debate tv home include millions watch online social media bar restaurants third debate ahead nov. election mark trump refusal commit accept outcome election republican candidate lose democratic rival challenge cornerstone american democracy presidential election debate hold las vegas moderate first time journalist fox news chris wallace give fox news cable channel lead number viewers debate 11.2 million follow broadcasters abc nbc 10 million viewers second third presidential debate generally attract small tv audiences many voters already make mind presidential campaign last year final trump-clinton debate draw nearly 72 million viewers third large ever