Kamala Harris supporters are seizing on a slip-up by Donald Trump as a “senile moment.” The former president referred to Republican Senate candidate David McCormick as Pennsylvania’s “future governor” while speaking about U.S. Immigration and Customs Enforcement officers during a rally in Harrisburg Wednesday, and he pointed to him later in the speech and referred to him twice as “Mr. Governor.” “They’re almost as tough as the man that’s going to be your next governor, by the way,” Trump said during the rally. “He’s tough too, he’s a great military hero.” Want more breaking political news? Cli…