Probably not the case, but Fallows' argument isn't too shabby:
For a candidate coming from behind, every second of the final week of
the campaign is like a second in cardiac-surgery operating theater,
with absolutely no room for fooling around or wasting time, money, or
effort that could be used to sway that last crucial vote. (Think: the
last days of Gore-Bush in 2000.)
For a candidate who thinks he's ahead, and might actually become president, inevitably there's a tone of new seriousness right at the end: What we've been working for years is within our grasp, let's not screw this up, and let's be sobered by how different the world is going to look in a few days.