On Friday, The New York Times reported that Kurt Volker, a State Department special envoy to the Ukraine, has resigned:

This comes as Volker, a longtime, widely respected diplomat, is facing a volley of questions about his involvement in the Ukraine scandal, in which Trump apparently pressured Ukrainian President Volodymyr Zelensky to help him dig up dirt on former Vice President Joe Biden.

In particular, Volker appears to have been in touch with Trump's personal attorney Rudy Giuliani about setting up the call — a fact that Giuliani himself confirmed on Thursday by releasing a text message exchange between them.