So, it just makes good sense for her to prep by watching the debate, and, I bet, any interview of Clinton that she can, to get the woman’s speech patterns and mannerisms down as much as possible.
Seeing as how political sketches are a big deal on SNL, Kate McKinnon will have to constantly keep her Hillary Clinton game up during the season.
It’s not impossible, with the election being so close now, that she could be called upon to play the presidential candidate on a weekly basis.
It would seem that the best way to realistically mimic someone who’s in the public eye would be to watch them and repeat what they say and do as often as you can.