The prevailing narrative at the Cleveland convention has not been about Trump's positions, but dominated instead by the failure of he party's various factions to unite behind Trump.

Trump wants to build a wall along the US border with Mexico, ban Muslims from war-torn Middle Eastern countries and renegotiate international trade agreements. He also says he would force US allies in Europe and Asia to pay more for the US defense umbrella. All those positions go against prevailing Republican beliefs.

A series of distractions has largely thwarted a bid by the Trump campaign to show him as a caring father and magnanimous business leader who would bring greater prosperity and safety to the United States.

Trump's wife, Melania Trump, made the biggest strides toward that goal. But when it was discovered her remarks repeated lines from a 2008 speech by Michelle Obama, the wife of the Democratic president, the uproar lasted for three days.

On Wednesday night, Trump's last major rival during the bitterly fought Republican primary battle, US Senator Ted Cruz, was booed off the stage for refusing to endorse Trump and urging Republicans instead to "vote your conscience."