My wife lived in NYC for over a decade and is a fan of Bloomberg and liked him as mayor. She watched the debate solely because Bloomberg was in it. She probably would admit he got destroyed especially the first hour.
However, I wouldn't guarantee Bloomberg is over. Being good or bad at debates isn't the end all be all.
Remember Kamala Harris? She did great at one of the debates and where is she now? Debating takes practice and Bloomberg was in his first debate in years and it showed. I don't know if he was too arrogant to listen to his advisors, (he seems to think he knows how everyone should live their lives and to think he is smarter than everyone else) but many of the questions could have been expected and his answers just didn't work. 1) apologize 2) release the women from the NDAs but do it by saying something like "if any parties with signed NDAs want to cancel the NDAs for both sides, I am willing to do that." If he knows what is in them is too damaging, then maybe he is screwed but he shouldn't have run for president then or come up with a better way to say he's not going to release them.
Perhaps he thought everyone wouldn't pile on him, but they did and that mean the big winner was ...Bernie Sanders. Bloomberg being in the debate was a gift to Sanders as is shifted the attacks off him.
Everyone wants to be the "moderate" who can take on Sanders and they forgot that Sanders is actually the front runner. So Sanders was the winner.
Didn't something similar happen with Trump? Cruz and Kasich and whoever were all fighting to be the one to take on Trump and instead of going after Trump went after one another. Maybe it was their only option but it favors the guy with the strong base which Sanders and Trump had.
And then I think that means Donald Trump was a winner as well. Trump has to love his chances vs Sanders.
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The other thing Bloomberg has is probably like $100 million to drop this week to try and change the narrative.