getting latest information on twitter and the a, you're abc news app and stay up to date on the late esinvitation. there's a major national story to talk about tonight as well that we're following closely. the countdown to the presidential debate and about an hour and a half to go. this will be the first face-off between hillary clinton and donald trump. the estimates are 100 million people will watch this debate. the audience could rival the super bowl in fact. abc news reporter marcy gonzalez is at hofstra university in new york with a preview of tonight's showdown. >> reporter: tonight, facing off for the first time. hillary clinton and donald trump taking on the issues and each other in the first presidential debate. >> the they have to actually switch positions. he needs to be less visceral and more rational and more head and less heart just like she needs more heart and less head in the course of this debate >> reporter: 90-minute showdown broken down into 15-minute segments with clinton going first. each getting two minutes to reply, and with the latest polling showing a close race, tonigh