"Fellow Republicans, there's still time to save your souls," Arizona Senator Jeff Flake began his September op-ed in The Washington Post

He then went on to urge Republicans to risk their careers in favour of their principles and not support President Donald Trump's 2020 election bid.

Flake, who retired from the US Senate in 2019, had a fraught relationship with Trump during the president's first years in office, but Flake's vote had been pivotal to the White House at times, including last year's confirmation of US Supreme Court Justice Brett Kavanaugh.

Flake joined United States Studies Centre CEO Professor Simon Jackman for a conversation about his experiences in US Congress and with the president, his views on the impeachment investigation and the 2020 US presidential election.