The Women's Vote.
Obama is up in the Colorado PPP poll. They didn't include third party candidates. If the polls included third party candidates, there'd be less undecided voters.
This poll surveyed a 53:47 ratio of women to men. That seems a little high to me. However, women do vote in higher numbers than men and that number appears to be rising.
The Center for American Women and Politics (CAWP), Rutgers University, which reports that:
* Women vote in higher numbers than men, and have done so in every election since 1964. In 2000, 7.8 million more women voted than men. In 2004, 8.8 million more women voted.
* Women outvoted men in every racial and ethnic group. For Asian/Pacific Islanders (but not for other groups), 2004 was the first election where women voted at a higher rate than men.
* More women register to vote than men.
Obama polls well among women. This does not bode well for McCain, especially in those key battleground states like Colorado.