WASHINGTON — President Trump escalated his attack on Senator Bob Corker on Tuesday by ridiculing him for his height, even as advisers worried that the president was further fracturing his relationship with congressional Republicans just a week before a vote critical to his tax cutting plan. Mr. Trump gave Mr. Corker, a two-term Republican from Tennessee and chairman of the Senate Foreign Relations Committee, a derogatory new nickname — “Liddle Bob” — after the two exchanged barbs in recent days. He suggested Mr. Corker was somehow tricked when he told a reporter from The New York Times that the president...