Like Meeker said, we'll have to wait for the full results to come in before we can give a more definite answer. However, during the last 12 days of the race, 5 separate polls showed Gregoire clinging to a 2 point lead over Rossi. Then,
a Survey USA poll released on the eve of the election showed a 6-point Gregoire lead. At the time, I mused whether it was an outlier or if the race was breaking in her direction. The results suggest that it was the latter.
There were two key differences in the poll Survey USA conducted on 10/28 vs the one released on 11/3. In the poll on 10/28, Rossi led young voters by 17% while Gregoire had a 5 point lead among women. Per the 11/3 poll, Gregoire pulled even with Rossi among young voters and powered to a 12 point lead among women.
While the Gregoire campaign was (with some justification) criticized as incompetent, they ran a large and aggressive ground game to GOTV. In Gregoire's victory speech she said they made over 1 million phone calls and knocked on over 250,000 doors. My brother said Gregoire had over 100 volunteers in the Beacon Hill neighborhood (in Seattle) contacting voters during the final push. She made a full-court press to turn out the base in King County. She also worked to tie herself to Obama (whom she endorsed in Feb.) which may have paid off.