And if Trump keeps attacking fellow Americans like he has, he will have no hope of a comeback. I think Clinton will have the whole deal wrapped up no later then the end of the second debate. Trump can only ride the negative for so long and his weaknesses will become quite clear, even to the deeply disatisfied of the country. He, and he alone, will lose the race to the White House since Republicans are already running the other way.
I don't think it's possible for Clinton to lose more people than she already has. She's been climbing uphill all cycle despite what the DNC would have us believe. However, Trump is starting to meltdown with the Khizr Kahn issue, and it's likely he has a full-scale explosion under pressure as the months go on. I expect Clinton to win.
Yes, the poll numbers could change drastically after the post convention bump has subsided. Barring any unforeseen crises, most candidates have a boost after a convention--even Trump did--but the boosts don't usually last. There are still several months until elections. Nearly anything is possible at this point--especially with the unusual circumstances of this election.
Hillary Clinton's lead in the polls seems solid. In the wake of the DNC, she received a bump in her poll numbers. However, this is more than just a post-convention bounce. Trump continues to inflict harm on himself through his statements, including calling out the parents of slain military man. His own party is criticizing him. People are afraid of a President Trump.