Impeachment proceedings have been launched against Donald Trump after a whistleblower said the US president pressured the leader of Ukraine into investigating one of his main Democratic challengers.

In a telephone conversation Trump asked President Volodymyr Zelensky to look into Joe Biden, the man Trump may well face in the 2020 presidential election, and connections Biden’s son had in Ukraine.

The whistleblower’s allegations mention Trump’s personal lawyer Rudy Giuliani as the person who was essentially running the Ukrainian evidence-gathering operation. Giuliani was the ‘hero’ mayor of New York, guiding the city through the horrors of 9/11. But now he’s seen as a more-than colourful character wheeled out to defend his boss to the end.

As the proceedings gain momentum, we ask The Atlantic’s White House correspondent, Elaina Plott, whether a phone call could bring down America’s most divisive president, and the details of a fiery exchange she had with Giuliani in the back of an Uber.

Presenter: Matthew Price