Former President Donald Trump is losing his mental acuity, “Art of the Deal” co-author Tony Schwartz told MSNBC’s Ari Melber on Thursday. This is more apparent than ever after he was crushed in the debate with Vice President Kamala Harris, Schwartz argued. “He is a very different man than the man in the late 1980s and the man I somewhat interacted with in the 2016 election and the 2020 election,” said Schwartz. “This is a man who’s lost a great deal mentally. He is not — this notion that he, that he is still, like, capable of exciting a crowd, I’m just not sure that I believe, beyond that 20 o…