As the GOP Convention gets underway, it will be interesting to see how any Trump bounce in the polls manifests. First, a positive bounce would require a convention that actually functions without catastrophe, crisis, or embarrassment for the Republicans or for Trump. That's not in the bag. Romney's campaign was well organized and well funded and, still, it suffered this at their convention.
Second, if the convention works more or less as it's traditionally supposed to, can Trump break the polling ceiling that to this point he's been trapped beneath and do so with any staying power? Have a look at Huffington Post's polling tracker, which does a good job a averaging polls from multiple outfits. The graph to this point is clear. The recent tightening of the race has been almost exclusively a result of Clinton's numbers dropping after Comey's statement about the email investigation. Trump's numbers have not improved significantly. Even in May when Trump had locked in his primary victory and Clinton and Sanders were still slugging at one another, Trump's poll numbers never got much higher than 42%. Clinton's have never dropped below 43%. If her floor continues to remain above his ceiling, it's a very good indicator of how the race will play out. If the convention can't raise the ceiling, few other events between now and November will either.