President Donald Trump urged the new leader of Ukraine to investigate the son of former Vice President Joe Biden.
The push to damage a political rival is at the heart of a whistleblower complaint that has created a showdown between Congress and the White House.
Two people familiar with the matter say the complaint was based on a series of events, one of which was a July 25 call between Trump and Ukrainian president Volodymyr Zelenskiy.
One of the people says Trump urged Zelenskiy to probe the activities of potential rival Biden's son Hunter, who worked for a Ukrainian gas company. The people were not authorized to discuss the issue by name.
Trump is angrily labeling the allegation as “partisan” even as Democrats move to investigate the interactions.