While I am course happy to talk to any Republican candidate, and I am more than happy to be handed a big stack of deniable, legitimate* oppo on any Democrat, I have come to the conclusion that participating in anonymous oppo against my fellow-Republicans and conservatives is… unwise. You get controversies. Agitation. People become… uncivil.
Best to avoid that.
PS: As to why Chris Wallace won’t reveal who gave him the oppo about Cruz (even if he should): that’s because this way everybody will assume that the oppo was sent over by The Most Powerful Republican That I Personally Despise. If it comes out that it was somebody on, say, the staff of a Beltway Bandit political group (which is where I suspect the oppo originated), people would stop getting ticked off at their favorite Hate Object. Remember: Chris Wallace is not our friend.
*I am a partisan hack; I just won’t lie. Which means that I don’t follow LBJ’s famous dictum to the letter; but if it’s at least plausible then sure, make the guy deny that he’s a pigf*cker.