Reasonable worst case scenario for the GOP: They lose the Presidential race, they lose control of the United States Senate by a few votes, and they lose a few seats in House of Representatives but retain control and they retain a majority of Governors and state legislative bodies.
Reasonable best case scenario for GOP: they win Presidential race, expand control of the Senate, retain control of the House and expand majority of Governors and state legislative bodies.
Reasonable worst case scenario for the Dems: they lose Presidential race, lose seats in the Senate, don’t gain control of House and lose more Governor’s and state legislative races.
Reasonable best case scenario for the Dems: win Presidential race, gain control of Senate by slim margin, pick up a few seats in House but don’t control, win a few Governor’s races and legislative seats.
So when you look at the various scenarios for the 2016 general election you reach the following conclusion: the upside for the GOP is much better than any upside for Dems, and the downside for the Dems is much much worse than any downside for the GOP.