From the Washington Post:
The shift in the race has come almost exclusively from female voters, who prefer McAuliffe by a 24-point margin over Cuccinelli. The candidates were effectively tied among women in a Washington Post poll in May.
McAuliffe’s strength among women is likely due in part to an intense campaign to portray Cuccinelli as a threat to women and the issues they care about most deeply. A new McAuliffe ad, for instance, features a Norfolk OB-GYN speaking directly to the camera about how she is “offended” by Cuccinelli’s position on abortion.
The challenge for Cuccinelli is stark: Nearly half of all voters view him unfavorably, and they trust his opponent as much as or more than the Republican on every major issue in the race, according to the poll. On trust to handle issues of special concern to women, McAuliffe leads Cuccinelli by 23 points.
Both candidates have very deep flaws (both have favourability numbers that are upside down) and they both have challenges which the article goes into more deeply, but it seems that Cuccenilli's negatives outweigh McAuliffe's.