In a US presidential contest between two of the oldest candidates ever to run for the of Oval Office, age has become one of the crucial questions hanging over the 2020 campaign.

So, what would happen if a newly-elected Joe Biden were to be taken ill and could no longer discharge the office of the presidency? If this scenario were to play out, of course, Vice President Kamala Harris would be sworn in as the next President of the United States.

This has the potential to change everything, says historian Niall Ferguson. Speaking at a recent Reaction event, Ferguson warned of the troubling consequences that could arise from Harris taking over the top job.

“The California Democrats are at that point in charge of the most powerful country in the world”, he says, a situation that he fears would be very dangerous.

“So those people who think that a landslide Biden victory will be the end of their troubles, that Mr Trump will go away and normalcy will be restored, I think they’re in for a big disappointment.”

You can watch the full video here on our YouTube channel.

The prospect of a Biden administration turning into a Harris presidency adds another dimension to this year’s extraordinary battle.