Warner will make the announcement at an event Wednesday with Clinton's running mate.
"As a result of Donald Trump’s huge debate win last night, we had a massive fundraising day," Trump's finance chairman said.
"You just block it out."
"It was obvious he wasn't prepared,” said one House Republican who supports Trump.
Trump said he didn't want to do anything to "embarrass" Clinton.
An adviser said Trump is doing the charity a favor by hanging a portrait in his hotel.
Sanders touted Clinton's education plans.
Trump was pushing back against accusations that he initially supported the Iraq War.
Trump is hosting a rally in Melbourne, Fla.
"Both are proven liars," he says.