>>1. He is deliberately teasing the press by leaving open the possibility that he was a cocaine user in his misspent "youth."
2. He thinks he's got everyone hushed up, but can't run the risk of getting caught in a lie.<<
Of course you wouldn't have thought....
OR #3. He went through a 12 step program to make a change in his life and his actions and is practicing what it says in one of the daily readings: "I am responsible for taking the actions necessary to keep myself safe. But when my safety is not at risk, I can take time to make choices about my responses. I don't have to react instantly to provocation, and I am not obligated to justify myself to anyone. By turning to God for protection, rather than my wits or my will, I avail myself of the best possible defense." And "When I am troubled about what lies ahead, I look back to see where I have been. Time offers me evidence that the program works - I can see the growth in my life. The longer I live by these principles, the more evidence I have. This reinforcement provides strong support in times of doubt and helps boost my courage in times of fear."
It could very well be that our president has learned from his past in order to achieve a better future, something that takes rigorous honesty, something that I do not see in you.