Author: Zachary B. Wolf, CNN

Trump's Ukraine scandal: Who's who?

The fast-moving scandal involving President Donald Trump and allegations that he pressured Ukrainian President Volodymyr Zelensky to investigate his political rival Joe Biden and his son, Hunter, has upended politics in Washington, DC, and evolved into a full-blown impeachment investigation. There is no evidence that either Biden did anything wrong.

How impeachment works

Calls to impeach President Donald Trump began among some Democrats almost the day he was inaugurated. They ballooned after former special counsel Robert Mueller's report to Congress about interactions between the Trump campaign and Russia and, separately, Trump's efforts to squash the investigation, potentially obstructing justice.