An angry crowd booed Texas Senator, Ted Cruz for failing to endorse Donald Trump as the Republican nominee, during a speech at the party convention in Cleveland.
Mr Cruz only went as far as congratulating the man who was his bitter rival in the primary contests.
Cruz began his speech saying: “I want to congratulate Donald Trump on winning the nomination last night.”
Later in the speech, he urged: “Please, don’t stay home in November. Stand, and speak, and vote your conscience, vote for candidates up and down the ticket who you trust to defend our freedom and to be faithful to the Constitution.”
Some critics saw the appeal for people to vote their conscience as a vote of no-confidence in Trump.
Republican strategist Eric Fehrnstrom, who is not affiliated with any campaign, tweeted: “‘Vote your conscience’ was the rallying cry of the Never Trump movement.
“For Cruz to bring that message into #RNC hall was a colossal error.”
“It’s taken me about 30 minutes to calm down and stop shaking with anger,” said Erik Layton, an alternate delegate from California who had shouted: “Go home” at Cruz after his speech. “I just don’t know why Cruz did this. It baffles my mind.”
But angry chants of “we want trump!” and “endorse trump!” grew louder as the senator came to the end of his speech.
Indiana Governor, Mike Pence then took centre stage to give his vice-presidential acceptance speech.
But analysts say Mr Cruz will steal the headlines after stoking the rage of the convention, to such an extent that his wife Heidi had to be escorted from the floor.