A few observations about the forthcoming presidential debates:
i) The first debate is usually the most watched and most influential. For many viewers, this is the first time that they are really tuning into the campaign. This is their introduction to the candidates.
ii) That will probably be accentuated in this case. Although Hillary is a known quantity to political junkies, I expect most Americans don't know much about her. She really hasn't been that much in public eye for years. She was most prominent as First Lady. After that, she a two-term NY senator, but that's inside baseball for the average American. After that she was Secretary of State, but unless you're a news junkie, most Americans couldn't name the Secretary of State. In the Obama administration, moreover, everyone plays second fiddle to Obama. He's the star. He's in every scene. Everybody else is an also ran.
So even though Hillary's extremely well-known to Americans who follow politics closely, I expect most Americans know more about Reality TV stars than she. She has tremendous name-recognition, but that doesn't mean most folks have in-depth knowledge of her political history.
And this will be even more the case with respect to her Republican counterpart. If it's Rubio, Cruz, or possibly Carson, unless you're a political junkie, the first presidential debate will be the first time that most viewers have seen them and heard them. This will be their first impression, for better or worse.
iii) Another variable is who hosts the first debate. If it's Fox, it will be more evenhanded. If it's CNN, it will be like The Cincinnati Kid where a cardsharp deals winning cards to Hillary. The Republican candidate has to be twice as good to overcome that handicap.
iv) And that, in turn, will depend on who's ahead in the polls, and by how much, when debate negotiations take place. If one candidate has a strong lead, then they dictate the terms of the debate. The candidate who's trailing must bargain from a position of weakness, since they need the debate to catch up or overtake their opponent, while the lead candidate can afford to walk way from the table.
The incentive of a candidate who's way ahead in the polls is to sit on their lead and play out the clock. They have more to lose and less to gain by a debate.
In addition, name-recognition, in itself, gives you a head-start, and that favors Hillary in the early stages of the campaign–which may spill over into debate negotiations. Name-recognition is a default setting for many voters.