Washington • Impeachment of a president is a deeply serious affair. Efforts by President Trump and his defenders to explain away his clear-as-day abuse of power are providing a bit of comic relief. The problem for the president and his amen chorus is that the White House released a document proving Trump guilty of an impeachable act. In the official memorandum of a July 25 conversation with Ukrainian President Volodymyr Zelensky — at a time when Trump was unilaterally withholding $391 million in military aid for Ukraine, which Congress had approved — Zelensky expresses a desire to purchase U.S. anti-tank missiles. Trump replies: “I would like you to do us a favor though.” Book him. The “favor” includes firing up an investigation of Joe Biden, the front-runner for the Democratic presidential nomination. Trump ignores U.S. national security interests and uses taxpayer funds as leverage to coerce a foreign leader into interfering in the 2020 election. For such conduct, he not only can