Sign up for the daily CJR newsletter. In February, President Donald Trump endorsed a proposal that would allow Nexstar, already the largest owner of local broadcast stations in America, to acquire Tegna, a smaller rival. “We need more competition against THE ENEMY, the Fake News National TV Networks,” he wrote on social media. “GET THAT DEAL DONE!” Last week, the Federal Communications Commission and the Department of Justice approved the merger. The resulting behemoth will control two hundred and sixty-five television stations, reaching 80 percent of US households—more than double the 39 percent national audience cap allowed by law. “It’s a grotesque violation of the cap,” Diana Moss, the vice president and director of competition policy at the Progressive Policy Institute, a liberal Washington think tank, told me.…