But there is one key similarity with those speaking out – they can’t be troubled by Mr Trump’s base, said US election analyst and ANU professor Wesley Widmaier. “Mitt Romney is a unique figure. He is a former presidential nominee, and he is incredibly respected in his state, he’s an elder finger in the Mormon church, he has no worry Trump could every threaten him,” Professor Widmaier said. “Lamar Alexander has been in power for 30 years and is retiring.” Many Republicans won’t publicly denounce Mr Trump’s behaviour because they don’t want to lose voters, Professor Widmaier said.

Key Republicans are speaking out against Donald Trump