Donald Trump’s meandering, convoluted and seemingly eternal speech closing out the Republican National Convention Thursday night wasn’t just evidence he’s unfit to lead the nation a second time, but the ramblings of someone suffering from serious mental illness,The Atlantic’s Tom Nichols writes. In the wake of his near-assassination, Trump had the opportunity to show a different side of himself and sway undecided voters to his camp. But instead of sticking to talking points about “unity,” Trump went mostly off-script as he delivered the longest acceptance speech on record, which included musin…