The public on Tuesday will get its first look at Army Lt. Col. Alexander Vindman in action. And if he follows his closed-door testimony, he will knock his commander in chief while retelling his version of potentially damning conversations with a Trump ambassador. “I’m the director for Ukraine,” Col. Vindman told the joint House impeachment panel on Oct. 29. “I’m responsible for Ukraine. I’m the most knowledgeable. I’m the authority for Ukraine for the National Security Council and the White House.” “I’m certainly not the president of the United States,” he said at another point, when asked by a Republican...