Trump lawyer Rudolph W. Giuliani says he’s uncovered proof of “extensive” corruption in Ukraine, including “clear” proof of money laundering by Burisma energy company and Hunter and Joseph R. Biden. In a series of tweets, Mr. Giuliani said his trip earlier this month to Ukraine “garnered witnesses & documents which reveal the truth behind this impeachment,” which he said includes no wrongdoing by President Trump. “Evidence revealed that corruption in 2016 was so extensive it was POTUS’s DUTY to ask for US-Ukraine investigation,” Mr. Giuliani tweeted, days before the House prepares to vote on impeaching the president. He said impeachment...