Lead story on Gallup:
John Kerry won the debate Thursday night, 53% to 37%, according to a random sample of 615 registered voters who watched the event. Almost half of the viewers said they felt more favorable about the senator because of the debate, and 60% said Kerry expressed himself more clearly than did President Bush.
The article goes into more detail, breaking down results by party and issue. 93% of Kerry supporters thought their man won the debate - no surprise - but among Bush supporters, the number drops to 68% for their candidate.