It'll be really hard to imagine how he will make Republicans lose races, especially next year when they are far more likely to gain than lose just by the map itself.
Yes, they're totally going to win more in a presidential year with several chances of having an unelectable presidential nominee dragging them down.
Well I mean look at the map:
West Virginia, Missouri, and Montana. All deep red states with outgoing Governors or moderate meh Governors. West Virginia is flipping Republican - Despite all the broohaha that this is going to be competitive, Bill Cole is not a complete flop and the state is moving so Republican that it won't matter how much money Jim Justice throws at this race. Missouri has a leaving unpopular Democratic Governor, and Republicans have a very strong up and comer in Eric Greitens, who will likely win the primary in my view. This is definitely more of a toss-up, but having the Republican win by 10 points or so on the Presidential ballot doesn't help Chris Koster. And Montana is probably the most toss-up of the three, with the incumbent being moderately popular/unpopular, but again, Republicans will win Montana big, that does not help Steve Daines.
There are some odd Democrat/Purple states where Republicans are competitive. New Hampshire has Chris Sununu running, who is definitely the favorite in this race. And Vermont has an odd history of supporting Republican Governors very recently - and Phil Scott fits the bill they have. I'd say odds are decently good both are won by Republicans.
Then we've got Republican weak zones - Indiana and North Carolina. Indiana's controversy will steadily go away, and when that's more in the rear view, the less chance John Gregg has against Mike Pence. Pence will underperform, guaranteed, but he will probably beat Gregg. If Republicans win North Carolina, I think Pat McCrory wins too. If Republicans lose it, McCrory loses as well. I think he lives by the sword, dies by the sword.
So yes, Republicans have a good chance of picking up seats in 2016.