President Donald Trump is under intense scrutiny over a classified whistleblower complaint about his behaviour, which at least partly involves his dealings with Ukraine's new president and Trump's call for Ukraine's government to investigate former Vice President Joe Biden, who is a leading candidate for the 2020 Democratic presidential nomination.
Here are some of the basic facts behind the controversy.
What did Trump do?
In a July 25 phone call, Trump is said to have pressed the president of Ukraine, Volodymyr Zelenskiy, to investigate Biden's younger son, Hunter, who sat on the board of a Ukrainian energy company. Trump has