538 had together with Ipsos some polling about the impact of the third debate:
https://projects.fivethirtyeight.com/democratic-debate-september-poll/
https://fivethirtyeight.com/features/the-third-democratic-debate-in-7-charts/
EDIT: Notable in my opinion is, that Castro got a lot more unfavorable (O'Rourke and Warren on the other hand gained a lot favorability). Bidens electability is seen a bit less secure. Overall it seems Warren is the biggest winner of the debate.
Last edited by Mnementh - on 15 September 2019