The exchange unfolded after the CBS News moderators asked Vance if he would try to challenge the results of November's election, even if every US state governor certified them - as was the case in 2020.

Vance did not directly answer, instead saying he was "focused on the future".

He sought to defend Trump over the riot during which President Trump's supporters attacked the US Capitol building in an effort to stop Joe Biden becoming president.

Vance said Trump had simply spoken of "problems" in 2020, and insisted that Trump had only said that "protesters ought to protest peacefully".

Turning to the outcome of the 2024 vote, he said: "If Tim Walz is the next vice-president, he'll have my prayers, he'll have my best wishes, and he'll have my help whenever he wants it."

But Walz persisted with the events of 2020 - challenging Vance to answer whether Trump had lost the poll. When Vance again sought to change the topic, Walz said: "That is a damning non-answer."