He blew CIA agent Valerie Plame's cover. Here's how he's going to cover that: HE WILL SAY: "ALL I TOLD REPORTERS IS THAT JOE WILSON'S WIFE RECOMMENDED HIM" (to check on the phony Saddam-Nigeria-uranium connection).
We are at war, declared by the president. Karl Rove, if he makes the above admission, caused the deaths of CIA operatives and compromised their expressed mission in the defense of the nation in that war. That would make him not just a felon but liable to prosecution for T-R-E-A-S-O-N (imagine Tammy Wynette or Aretha Franklin singing that out).