Hours before the presidential debate began in Sunday, former New York Mayor Rudy Giuliani invoked St Augustine of Hippo on a Sunday morning political news show to defend the man he was supporting for president.

"Ever read 'The Confessions' of St Augustine?" Giuliani asked John Dickerson, the host of "Face the Nation," referring to the autobiographical book about St Augustine's sinful past and his subsequent conversion. "Men can change, people can change."

Hours later, Donald Trump, the embattled Republican presidential nominee he was defending, was defiant in St Louis during the second of three presidential debates against Democratic opponent Hillary Clinton.