The concept of faking a weakness is an age old strategy. Feigned retreats have been utilized by armies since ancient times. I'm partial to Dan Carlin's description the Mongol use of this tactic. For those who have not yet listened to his excellent telling, the mongols would pretend disarray and retreat and run. Most of the killing in ancient warfare occurred during the retreat, so the Mongols would be chased in a less than fully organized fashion. Once the enemy lines were stretched out in pursuit the Mongols would turn on the pursuing army and deal them a devastating blow.
A similar stratagem is used in modern politics. Every candidate in this day and age has strengths and weaknesses. But the public does not have a large enough attention span to cover multiple topics. The best line of attack is to find a flaw in the candidate that is representative of their many problems and push hard when it appears they are weak.
Sometimes the weakness is not real. In 2008, some people thought that the allegation that Obama was not born in this country could be that type of attack. This attack was never going to work. Obama might have been ruled a natural born citizen of the United States no matter where he was actually born as his mother was from Wichita, Kansas. Furthermore, the long and short form birth certificates proving that he was born on US soil definitely existed. But rather than fully confront this attack when it first appeared to be growing he feigned retreat. The allegations were called racist and insulting and not worthy of response.
In fact, the allegations being labeled as racist and insulting created a good incentive for him and his team to not respond immediately. Not responding in Obama's birther case served many purposes. First, it was a refusal to give any respect to a group of crazy people attacking him. Second, it made many of his opponents look bad. Demanding the birth certificate of the first non-full caucasian president appeared quite racist. But more importantly, it filtered some of the most enthusiastic attackers of Obama into focusing on an issue that he knew would not get out of control. At a time when his advisors with Wall Street connections might have been vulnerable to attack or the handling of the stimulus might be critiqued the birther movement's existence encouraged many of his critics to instead focus on running directly into a brick wall.
Over time, the refusal to fully parry the birther movement created its own suspicion and attracted additional curiosity. The White House was forced to release his longform birth certificate to end it. But between 2008 and April 2011, a lot of his critics were charging at windmills rather than challenging him on policy.
Hillary Clinton's Wall Street speeches could be seen as a similar feigned weakness. When she was fending off Bernie Sanders from the left, the transcripts were a real weakness. But once she was past the primaries and moving towards the center for the general the speeches were no longer a large negative. Their release might impact enthusiasm among younger Bernie supporters, but that's about it. But by refusing to release them she created a feigned weakness for Trump and others to attack her. Considering her long history of controversy, any efforts here only served to reduce time spent on issues where she is potentially vulnerable.
In Clinton's case, Wikileaks released these speech notes sooner than she would have liked. It was unfortunate for her team not because the releases exposed anything too nefarious (though supporters on the left might be upset to learn that she is an anti-pot candidate), but because the emails were a feigned weakness that could soak up a significant percentage of attacks.
So the next time you see a politician refusing to counter an attack that seems easily parried if they are innocent, consider the tactical implications. Perhaps they want more of their critics charging at windmills.
Or maybe they really are hiding something. They're politicians, after all.