You don't see how it's possible? They will cheat, just like they've tried to do in the most recent general elections. A lot of the cheating was miraculously prevented due to some pretty dedicated efforts by some very extraordinary people. But it feels like a lot of that stuff was able to be implemented by Republicans in the off election years, which means that the chances of the Dem nominee (likely Hillary) ends up participating in a fair and clean process, is highly unlikely.
The only hope the Republican Party has of winning this election is they will have to cheat. There is no ifs, ands or buts about it. It's obvious why they win the mid-terms because there simply isn't nearly as much motivation for most of the country to go out and vote, which means they mostly win by default.
We need to be on the ball about that kind of voter disenfranchisement. That cheating. Gotta get that cell phone footage out there of the long lines, the confusing flyers, etc. Take the cameras into the voting booths when things are looking shifty. Make it obvious to them that they are being watched and put the pressure on them. And do it early.