There are backward hillbillies all over the U.S. who won't vote for a woman unless she has a firmly established brand name, and Hillary's got it. Also her husband is on the ticket.
If the first female president falls flat on her face then it will be almost impossible to get another woman elected for a very long time. Hillary has been in D.C. for so long that everyone already knows what her strengths and weaknesses are, and her husband and staff know it, too, and so they'll hire reinforcements. In other words, voters who are still angry because Hillary didn't answer the phone at a critical moment will be assured that it will never happen again. Those who suspect that she copied other senators' votes when she was a senator will be assured that she'll do her own homework when she's in the White House. Her longtime staff and husband won't let her fall down.