Wordsmith Bill Quick (who coined the term "Blogosphere") at Daily Pundit offers a vocabulary lesson:
"A fast and dirty indicator that a commentator doesn’t have much use for Donald Trump is the frequent use of the term “presumptive nominee” to describe him.
"This usage was given an official benedication when Reince Priebus made the statement that Trump must be regarded as the presumptive nominee.
"Clue: Reince Priebus is no Trump fan, either."
Do go over and read the whole thing. There's serious history behind it, and the distinctions are worth remembering for future elections, too.
Awareness of both etymology and connotation are essential if we are ever going to start reclaiming the language from the distortions of the Marketing Class.
5/27/16 Update: Bill has added another post that further analyzes the subtle differences in connotation of these words (what I call "deep grammar") in the post titled "Presumed Versus Presumptive".