Sixty-six percent of Clinton supporters, registered Democrats who want Clinton as the nominee, are now backing Obama. That’s down from 75 percent in the end of June. Twenty-seven percent of them now say they’ll support McCain, up from 16 percent in late June.

“The number of Clinton Democrats who say they would vote for McCain has gone up 11 points since June, enough to account for most although not all of the support McCain has gained in that time,” says Holland.