See, traditionally people who make up their minds late in a campaign don't change it again before voting. So when the needle moves in the last six or eight weeks of a campaign, it usually stays where it is until the election.
It's starting to look as if the facts are once-again dominating what the 'Crats SAY about the facts in terms of how they are affecting the undecided voters. The undecided have been waiting for a long time and once they choose, they are saying, "O.K., I've seen enough. Terminus est."