By the same argument you would say that Cruz or Rubio should win.
Obama won in large part because he had superior campaign organization both to Clinton and to McCain.
That's also why I think Clinton will win this time around - the republican side is way too fractured to pull together behind one candidate. Trump seems unelectable given his unpopularity with general elections voters. Cruz seems to have alienated the party machine to the point that people joke about voting for Sanders before voting for him. Rubio is as conservative as Cruz but acceptable to the establishment and seems like the only one that everybody can get behind, but so far he seems to have less support and money than Cruz.
Clinton vs. regular republican nomination should be a toss-up given the fundamentals of the race (no incumbency, average economy, demographics). But it seems that Rubio will have a pretty hard time getting to the nomination and doing so may still cost him enough Trump/Cruz supporters to lose the general election.
Still the votes next week will show exactly what do Trump's numbers mean. It could turn out that they do not translate to real votes.