Ukrainian leader. This is the WaPo's latest report published this evening.
"One source familiar with the contents of the phone call said that Trump did not raise the issue of American military and intelligence aid that the administration was at the time withholding from Ukraine — indicating that there may not have been an explicit quid pro quo expressed in that conversation."
https://www.washingtonpost.com/national-security/trump-pressed-ukrainian-leader-to-investigate-bidens-son-according-to-people-familiar-with-the-matter/2019/09/20/7fa39b20-dbdc-11e9-bfb1-849887369476_story.html
"The latest 'smoking gun' Democrats have been clinging to in search of that ever-elusive Trump impeachment may have just imploded - after the Washington Post quietly reported on Friday evening that a July 25 phone call between President Trump and Ukrainian President Volodymyr Zelensky did not contain an explicit quid pro quo if Ukraine launched an investigation into former Vice President Joe Biden's son as initially reported."
https://www.zerohedge.com/geopolitical/did-trump-biden-ukraine-drama-just-implode-wapo-reports-no-quid-pro-quo-offered-during