Dave Weigel explains modern politics in a single sentence:
Voters are aware of a border crisis, they are aware that Barack Obama is president—they blame him for nothing getting done.
Yep. Republicans can basically do anything they want and never get blamed for it. Most voters don't even know who's in control of Congress anyway. When something goes wrong, all they know is (a) something went wrong, and (b) Barack Obama is the president and he should have done something about it.
That being the case, what incentive do Republicans have for making things go right? Pretty much none. This is, roughly speaking, a fairly new insight, and it explains most of what you need to know about American politics in the Obama era.