content: It's not so much a trick as it is having first hand knowledge of what's going on.  If the Dems. didn't have anyone on board with this, they may not have first hand knowledge of what is being said.  It's similar to having John McCain sit in on every Rep. meeting, then reporting back to the Dems. exactly what the Rep. agenda will be.  It's much easier to counter your opponent when you know exactly what your opponent will be doing.  At least this is why I believe those two Dems. are on board with this.