Five years ago today, Donald Trump and a mob of his supporters urged Congress to do what voters and courts would not: Allow him to rule over a country whose people had rejected him. Trump learned in the final days of his first term that the Constitution is riddled with ambiguities, loopholes and untested limits. And in the years since, he learned it's nearly impossible to punish a president who decides to test them. In fact, he was rewarded with a second term and a powerful, Supreme Court-issued form of immunity from prosecution.