The fourth Democratic primary debate will take place tonight in Ohio, with 12 candidates going head-to-head.

Elizabeth Warren looks to be in the strongest position, having moved into the lead in the latest polls. Joe Biden is a close second, though his son Hunter's TV interview about the Ukraine debacle could have an impact.

Meanwhile Bernie Sanders is back in the race after his recent heart attack, insisting that it will not slow down his campaign.

Cal Thomas and Marion McKeone assessed their chances in our US slot.

Listen to the interview in full by pressing the play button on this page.