I want to suggest something the 2016 election does teach us: persistent, obsessive investigations pay off. In the 90s, Republicans started investigating Whitewater. Even Ken Starr knew there was nothing to this after a couple of years, but he was put under pressure to keep at it, and eventually he hit some fluke paydirt: Monica Lewinsky. This had nothing to do with Whitewater, but who cares? Scandal is scandal, and it rubbed off enough on Al Gore that Republicans took back the presidency in 2000.
Fast forward to 2012. Hillary Clinton did nothing wrong related to Benghazi. That was clear pretty quickly, but Republicans kept at it. I laughed at them at the time, but they had the last laugh when they once again hit a fluke bit of paydirt: Clinton’s private email server. Clinton didn’t really do anything seriously wrong here either, but it didn’t matter. Republicans kept at it for the next year and a half, and that was enough to convince a lot of people that Clinton was, somehow, corrupt and untrustworthy. That allowed Republicans to retake the presidency.