WASHINGTON — President Trump is under intense scrutiny over a classified whistle-blower complaint about his behavior, which at least partly involves his dealings with Ukraine’s new president and Mr. Trump’s call for Ukraine’s government to investigate former Vice President Joseph R. Biden Jr., who is a leading candidate for the 2020 Democratic presidential nomination.
Here are some of the basic facts behind the controversy.
What did Mr. Trump do?
In a July 25 phone call, Mr. Trump is said to have pressed the president of Ukraine, Volodymyr Zelensky, to investigate Mr. Biden’s younger son, Hunter, who sat on the board of a Ukrainian energy company. Mr. Trump has seized on an unsubstantiated theory that Mr. Biden was trying to protect the company from prosecution when he called for the firing of Ukraine’s top prosecutor in 2016. Rudolph W. Giuliani, one of Mr. Trump’s personal lawyers, has pushed the Ukrainian government to investigate the matter.
Why is this coming up now?
Because of an intelligence community whistle-blower who filed a complaint last month about the president’s actions. An inspector general deemed the complaint “credible” and “urgent” and forwarded it to the acting director of national intelligence, Joseph Maguire, who has refused to share it with Congress. The issue was brought into the open when the House Intelligence Committee chairman, Representative Adam B. Schiff, Democrat of California, sent an angry letter to Mr. Maguire on Sept. 10 demanding the complaint be shared with his panel.
What did the whistle-blower claim?
The full extent of the whistle-blower’s complaint, as well as the whistle-blower’s identity, is not publicly known. Reporting by The New York Times and others has established that the complaint involves Mr. Trump’s interactions with Ukraine and a phone call with a foreign leader — possibly, but not necessarily, Mr. Zelensky. It is not clear if it includes other matters.
Did Mr. Trump use American foreign policy to pressure Ukraine to investigate a political rival?
This is the big question. The White House this summer blocked a package of military assistance to Ukraine. The aid was intended to help the country defend itself from Russian territorial aggression, including a military conflict in eastern Ukraine that has killed more than 13,000 people since 2014. The delay of the aid was first publicly disclosed about a month after the July phone call between Mr. Trump and Mr. Zelensky. Mr. Trump is not known to have openly linked the aid — which has since been released — to his demands for political investigations, but many Democrats believe that may be the case.
What does Mr. Trump say?
The president insists that he has been unfairly accused, saying — without offering evidence — that the whistle-blower is “partisan” and that Democrats and the news media are initiating a new “witch hunt” against him. Mr. Trump has said that he is aware that his conversations with foreign leaders are monitored by numerous government officials and that he would not incriminate himself so easily.
What is Mr. Giuliani’s role in this?
Mr. Giuliani has communicated with Ukrainian officials for months about the Bidens, as well as about the circumstances of the 2016 disclosures of payments earmarked by a Russia-aligned Ukrainian political party to Paul Manafort, Mr. Trump’s 2016 campaign chairman, who is now serving a prison sentence on charges related to his Ukrainian political work. Mr. Giuliani has sought information about both subjects, and traveled to Madrid this summer for a meeting with one of Mr. Zelensky’s top aides, whom he urged to investigate the matters.
Did Mr. Biden do something wrong?
There is no evidence that Mr. Biden intentionally tried to help his son when he pushed for the dismissal of the Ukrainian prosecutor, who was widely seen in the West as corrupt. Stamping out high-level corruption in Ukraine has long been a central goal of United States policy toward the country, and a standard condition for Western aid. On Saturday, Mr. Biden said he had never spoken with his son about any overseas work.
Mr. Biden played a lead role in the Obama administration’s diplomacy with Kiev, but Obama administration officials worried that his son’s work for the energy company, Burisma Holdings, could create at least the perception of a conflict of interest.