Why did it take 2 months to release Hillary's MoveOn slam?

[tinrobot]

The tape reported on by the Huffington Post was recorded right after Super Tuesday. That was over 2 months ago. Obviously, someone held on to that recording for quite a while. It's not coincidental that it came out right before the PA primary.

Since it was recorded in a room full of her supporters, does that mean one of her supporters held on to it and released it only now -- perhaps as a way to hurt her chances in Pennsylvania and hasten her exit from the race?

It could also be that the Obama campaign (or an Obama supporter) had the tape and held in reserve until they needed more ammo.

Just speculating, but it's interesting, regardless.