attorney that may become one of the focal points of the impeachment inquiry. the tweet, where rudy giuliani says he acted in the ukraine affair as the president's attorney to defend him against, quote, false charges. harvard university's professor laurence tribe is joining me now for the latest on his opinion of what giuliani's tweet spells trouble -- how it spells trouble for the president. tweeted out saying this is nothing less than the president was shaking down president zelensky not for the nation's benefit, but for the political benefit of donald j. trump as rudy's private client. laurence tribe is the author of "the power of impeachment." he joins me tonight. you said giuliani's tweet is nothing less than a confession the president was, in your words, shaking down the ukrainian president, not for the benefit of the u.s., but for his own personal benefit. can you explain what you mean by that? >> basically, rudy giuliani has