joining me from moscow, moscow correspondent fred weir. why do you think putin decided not to retaliate? what's going on here? >> well, it is a remarkable departure from diplomatic tradition. i mean, i can't think of a single case where an expulsion like that wasn't met with a mirror image, tit for tat expulsion. i don't think it's ever happened before. so putin is clearly making a calculation. that he doesn't want to poison the well, build up the acrimony, which of course, any kind of mirror image response would do. he wants to keep the field clear. maybe he's handing donald trump a victory, because trump can say, see, i'm spreading good will even before i take office. he's clearly calculated this. it's smart, i think. but he's playing out the clock until that three-week horizon