Yes, according to Dershowitz the other night, you really cannot have obstruction of congress from the executive branch.
He also said that Congress is exceeding their constitutional mandate of High Crimes, so they are the ones actually committing abuse of power.
Technically, he said that congress can't have obstrucion on it's own power and say-so. It needs the courts to compel testimony and THEN get a refusal from executive.
No matter. The public is ignorant of how government works, and most DEMs will believe whatever their liars tell them to believe.