Trumps's incessant sniffing in the first debate prompted Democrat and Physician Howard Dean to speculate that he used cocaine. Of course this hands off diagnosis got a lot condemnation from friend and foe, but Dean noted that Trump's grandiosity and delusional rhetoric also fit the pattern.
He does seem a bit to healthy to be a 70 coke addict, but that does suggest a question. These days, you probably can't get a job bagging groceries without taking a drug test. Why not political candidates at all levels? Submission of tax returns should also be mandatory.
Some alternative explanations for the sniffing include allergies and pregnancy.