evidence: Here are six key takeaways from the debate. [...] On migrants coming into the U.S. illegally, he said: "These are the people that she and Biden led into our country, and they’re destroying our country. They’re dangerous." [...] "Where is our president? We don’t even know if he’s the president," Trump said toward the end of the debate. "They threw him out of a campaign like a dog. We don’t even know. Is he our president? We have a president that doesn’t know he’s alive."