A spokesman for defeated Senate candidate Republican Roy Moore is ruing a catastrophic interview he took part in with CNN news anchor Jake Tapper.

Ted Crockett, a former Alabama commissioner, was interviewed as voting was under way in a tightly fought contest to elect the state's new senator.

During the interview Crockett passionately made the case for voters to support Moore, a former state judge, who has been embroiled in a scandal over sexual misconduct claims.

On air, Crockett was forced to defend Moore's claims that Muslims could not serve political office in the United States as they would have to swear on the Bible, contradicting their own religious beliefs.

"You have to swear on the Bible," said Crockett. "I had to do it. I'm an elected official three terms. I had to swear on a Bible. You have to swear on a Bible to be an elected official in the United States of America. He [Moore] alleges that a Muslim cannot do that, ethically swearing on the Bible."

But Tapper immediately refuted the claims. Candidates must be sworn into office but how they do so is entirely up to them, he said.

"You don't actually have to swear on a Christian Bible, you can swear on anything, really," Tapper replied.

"I don't know if you knew that. You can swear on a Jewish Bible. The law is not that you have to swear on a Christian Bible. That is not the law. Did you know that?"

Crockett seemed stunned by the information. In his faltering response he says: "I know that Donald Trump did it when we made him president."

The excruciating interview was replayed widely on social media with some claiming Crockett was lived in an "echo chamber." Here is just some of the social media reaction:

Roy Moore was defeated in the poll, losing by a margin of 49.9% to 48.4%. The winner, Doug Jones, now becomes the state's first Democratic party senator in 25 years.