Billionaire Donald Trump has been heavily criticised for refusing to repudiate an endorsement from racist group the Ku Klux Klan.
The 2012 Republican nominee Mitt Romney added his voice to a growing chorus of disapproval after the man leading the race to become the Republican presidential nominee hesitated during a Sunday morning political talk show to distance himself from the endorsement of former KKK grand wizard David Duke.
The property and entertainment mogul had repeated opportunities during his interview with CNN host Jake Tapper on the news channel's State of the Union programme to reject Mr Duke's support.
“I don’t know anything about David Duke, okay? I don’t know anything about what you’re even talking about with white supremacy or white supremacists. So I don’t know,” he told Mr Tapper.
He said that he was being asked to condemn a group that he knows nothing about. “I would have to look,” said Mr Trump.
Mr Romney, who has not yet endorsed any Republican candidate, described Mr Trump’s response as “disqualifying and disgusting”.
“His coddling of repugnant bigotry is not in the character of America,” tweeted the former Massachusetts governor.
When asked about his comments on NBC’s Today programme on Monday, Mr Trump blamed a “lousy earpiece” provided by CNN during the interview from Florida for not being able to hear properly.
Poll topper
Despite his hesitancy in the Sunday interview, he had disavowed Mr Duke’s support at a press conference on Friday, he said.
Another poll has showed Mr Trump dominating the Republican race as he enjoys momentum from consecutive wins in three of the early state-nominating contests: New Hampshire, South Carolina and Nevada.
He topped the latest nationwide CNN/ORC poll by more than 30 points, with 49 per cent support. Florida senator Marco Rubio received 16 per cent, Texas senator Ted Cruz 15 per cent, retired neurosurgeon Ben Carson 10 per cent and Ohio governor John Kasich 6 per cent.
Polls by Monmouth University put Mr Trump ahead in Alabama and Oklahoma, two states out of a dozen voting today in the first multiple-state ballots in the US presidential races for the two parties.
Mr Rubio, who has stepped up his attacks on the New York businessman in the hope of chipping away at his lead, said Mr Trump’s responses to the KKK questions “makes him unelectable”.
“How are we going to grow our party with a nominee that refuses to condemn the Ku Klux Klan?” he asked.
Continuing his anti-Trump tirades after mocking his “small hands” and alleged spray tan at the weekend, a hoarse Mr Rubio called out Mr Trump’s sketchy detail on policies and dismissed him as a barking dog.
"We cannot elect a dog that caught the car," he told supporters at an eve of "Super Tuesday rally in Tennessee. "What is he going to do when he catches the car; we can't risk it."
The businessman picked up his first endorsement from a sitting US senator when Alabama Republican Jeff Sessions, an outspoken opponent of illegal immigration, backed Mr Trump on Sunday.
“A movement is afoot that must not fade away,” said Mr Sessions after donning one of the billionaire’s Make America Great Again caps.
