When one speaks of a normal curve or distribution, one is usually thinking of a relatively standard bell curve:
The thing about grading on a curve is that there is still a distribution with some high, some medium and some low. Grading on a curve does turn a mediocre grade into a somewhat less mediocre grade. With a sharp policy wonk like Hillary Clinton in the race, Trump will never get an A as she sets the top of the curve. The real question is where does curving really put Trump? And my problem with his analogy is this: no matter how much curving is done in a typical class, an F student who does not attend class, does not do the reading, does not complete assignments, fails the tests, and occasionally punches the teacher does not get curved up to a B or B+ or a C-. They stay an F. Because a hyper-low performer sets the bottom of the curve just as a hyper high performer sets the top.
So, the press really has been doing something to keep Trump in a state of false equivalence with Clinton, but this pedantic prof says: it ain't curving the grade. It is something else alright, but a student at the bottom of the class remains there, curve or no curve.