When the DSCC started pummeling Elizabeth Dole in August, this election became pretty much solely a referendum on her.
Dole could have survived that. North Carolina voters really liked her the first time she ran in 2002 and I don't think that really changed all that much in the last six years, even if some think she has not been a particularly good advocate for the state.
The problem is that instead of responding by putting Dole on the air, talking straight to the camera and saying that the ads were unfair and talking about what she had accomplished for North Carolina, her campaign just ran a bunch of mediocre negative ads against Kay Hagan, a politician we're probably going to be sending to the US Senate in two weeks who most North Carolinians know very little about.
The Dole response completely missed the boat: the election at this point has little to do with Kay Hagan and everything to do with Elizabeth Dole. The Dole campaign needed to respond to the DSCC attacks by reminding North Carolina voters why they like(d) Elizabeth Dole. But they didn't do that, and at this point it's probably too late. They let the DSCC define Dole in the voters' minds, and her campaign was way too slow to put its best asset- the candidate herself- forward so that she could try to redefine herself.
Dole could still win, but it's looking increasingly unlikely.