While Congress is vitally important, we also need more state legislatures OUT of Republican hands. They are perilously close to being able to implement their frequently floated fringe fantasy of calling a Constitutional Convention and re-writing the Constitution to do away with all the pesky bits they dislike: preventing the establishment of a state religion, freedom to criticize the President, etc.
This seems more than a little paranoia-based, to be honest. That would send approval of Republicans way down, and they know it.