I think the month of June is the month we are going to look back at where Donald Trump really lost a lot of his chance at becoming our next president.
His chances of winning the Oval Office were already fairly small for a major political party nominee in mid-June (~30%), but one would probably expect that if an underdog like Trump wanted to a more contentious bid for the White House (40-50% chance), he'd likely have to carry some of his momentum from his primary win over into the general election season.
Instead, we've seen the opposite. He has found himself in middle of numerous self-inflicted controversies, his poll numbers have plummeted, and his campaign has done an embarrassingly bad job of raising money. His campaign is no where near as established, sophisticated, or as large as Hillary Clinton's campaign. His ground game has a lot of work to catch up in some of the key swing states if he wants to have a better shot at winning this.
It was a bad June for the Donald.