I don't see them 'surrendering' the White House.  Even in Oregon, as close to a one-party State as there is, someone still runs for Governor.  

There is no monolithic US-wide Republican Party just as there is no monolithic US-wide Democratic Party.  17 Republican candidates and Bernie's strong showing shows that. 

The fact that right now the polls give Trump and Clinton 37% each or 42% each of the likely voters shows that either party still has that shot at the White House.