Part of the reason for skepticism is this:
In accordance to the RealClearPolitics tracking of the delegate count (found
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), most of the victories Bernie has had thus far (with the notable exceptions of Minnesota, Kansas, and Vermont) had a delegate margin of less than ten. Meanwhile, Hillary commonly wins with margins more than twice than what Bernie wins in those same states. Already he has a problem of even catching up with Hillary when his wins end up being less significant in those terms. To compound the problem, Hillary has a 9 percent lead (in the smallest lead mind, and also mind these polls usually have a ~5% margin of error, so the lead could very well be less than this) in Ohio, an upper twenty lead (again the smallest one) in Florida, and an average ~20% lead in North Carolina (there's one poll that has a 10 percent lead there, but it's from back in February, so I doubt it holds as much validity anymore). There are two states of interest however: in Illinois, Bernie is extremely close to Hillary (one poll actually has him winning by two percent, so essentially it's anyone's game there), and Missouri literally has only one poll (at least that's available through RealClearPolitics), thus I think that that state's also up in the air. Thus, the best bet for Bernie is to pull a second historic win in Ohio and also win Illinois while not falling too far behind in Florida, Missouri, and North Carolina. However, the problem is that his wins in Ohio and Illinois will probably be more narrow than Hillary's in Florida, Missouri, and North Carolina, meaning that while Bernie will continue his momentum, Hillary will be much closer to cinching the nomination (I mean, she already has more than half of the delegates needed for nomination, while Bernie doesn't even have half as many as she does (this naturally includes the superdelegates mind you)). Mind, I'm still hopeful for Bernie to begin his comeback and win the nomination, but at the same time I can't be delusional about his chances here :/. Stranger things have happened, but one best not hope for the strange to happen.
A link to the polls mentioned can be found
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. The link leads to the polls of Illinois, given that that's the most contested race at the moment. The rest of the polls can be found through the links above the polls. Perhaps I'm being erroneous in my interpretation here, in which case I'd love to be illuminated as to these errors

.