So are the resignation of Billy Shaheen and Hillary Clinton's apology to Barack Obama proof that the Clinton campaign really regrets that Shaheen brought up Obama's past drug use the other day? You be the judge.

On "Hardball" Thursday night, Clinton strategist Mark Penn brought up the word "cocaine" in a discussion about Obama's past drug use. And then, in an exchange with John Edwards strategist Joe Trippi that looked like a Mac vs. PC ad gone bad, Penn tried to suggest that he hadn't mentioned the word at all.

From the transcript:

Chris Matthews: These comments that are coming out of your campaign from different directions -- and I'm not sure how they're coming, nobody does -- but going after his perhaps youthful drug use, which he admitted in his book, and going after comments he made as a kindergarten student, at the age of 5 ... do you think those are appropriate shots at the opponent or are they below the belt?

Penn: Well, I think we've made clear that the issue related to cocaine use is not something that the campaign was in any way raising … I think that's been made clear. I think this kindergarten thing was a joke after Senator --

Joe Trippi: He just did it again! He just did it again!

Penn: This kindergarten thing after what the senator did ...

Trippi: Unbelievable ... He just literally --

Penn: Excuse me.

Trippi: No, no, no, Mark, excuse me. This guy's been filibustering this thing. He just said "cocaine" again. It's like --

Penn: I think you're saying "cocaine," I don't know. I think you're saying it.

Trippi: You just did, and I think there's something wrong ...