So Fitz says impeachment proceedings against Blago could interfere with criminal prosecutions.
Fitz has his job: putting bad guys in jail. The Illinois Legislature has its job: getting rid of a corrupt governor via impeachment. If doing their job makes it harder for him to do his, that’s not their problem.
Same is true for Congressional corruption: I would give absolute priority to expulsion over prosecution. There’s no Fifth Amendment issue raised, since an expulsion or an impeachment carries no criminal penalties. The accused has the right to remain silent, and the legislature can properly draw adverse inferences from that silence. And neither expulsion nor conviction on impeachment requires proof beyond reasonable doubt, or even the commission of a legally cognizable crime. (Not showing up for work is hardly a criminal matter, but if a President simply stopped doing his job that would surely be the sort of “high misdemeanor” – where “high” means “state,” as in “high treason” – the Constitution provides for.)
The Framers never imagined a federal law enforcement machinery powerful enough to bring down a sitting Member of Congress. That’s the reason they committed Legislative Branch discipline to the two Houses. Congress has been slacking off in that regard, in part by hiding behind the criminal process. But Constitutionally, that’s just completely upside down.