https://www.electoralintegrityproject.com/the-year-in-elections-2017
Corruption and Coercion: The Year in Elections 2017
Pippa Norris, Thomas Wynter and SarAH Cameron
March 2018
The study you linked has this though, and it's astounding ...
Nor surprisingly, public trust in American elections fell sharply; for example, the Gallup World Poll reports that in 2016 a third of Americans (30%) expressed confidence in the honesty of their elections, down from a majority (52%) a decade earlier.85
That is not what I would call "public confidence in the election system." That is the public epressing they believe the election system is not honest.
Thanks. Interesting.