All of the emails you can drum up, and all of the Benghazi hearings, won't hold a match stick to Treason, Obstruction & Lies.  They have plenty of evidence of that right now.  Starting with this.  An 8 minute FOX News video that describes the contact Trump surrogates had with not only the Russian Ambassador but with Russian intelligence agents during the campaign season, including the very day that DNC databases were getting hacked into. (This after the Trump adminstration denied that anyone had any contact with any Russians (5 times) during the campaign season.)
https://youtu.be/RKjK2fiZLVA

If Republicans can do 8 investigations into Benghazi, it's not hard to imagine what Democrats will do with Treason, Obstruction & Lies when they take over in 2018.