Yeah, they know
"Democrats' polling must be showing something similar (to the national polls showing major public disapproval of the health care bills). Otherwise, House members wouldn't have competed for permission to vote against it, Senators wouldn't have demanded nine-figure payoffs to vote for it, and Harry Reid wouldn't have held the vote on a Saturday night."
It also explains the urgency in getting a vote before Christmas break, as they know that it will lose votes rapidly as we enter an actual election calendar year. Which is kind of odd, really, the thought that voters will forget what happened in December but not what happens after January 1.