NEW YORK • Mr Donald Trump launched a full-blown attack on Republican rival Ted Cruz on Wednesday, accusing him of stealing victory in the Iowa caucus as the Texas senator hit back, rubbishing the mogul's presidential credentials and questioning his sanity.
Fighting back from second place in this week's caucus, Mr Trump lashed out on Twitter, telling his six million followers that the evangelical conservative had won the first vote of the 2016 election by fraud.
"Ted Cruz didn't win Iowa, he stole it. That is why all of the polls were so wrong and why he got far more votes than anticipated. Bad!" Mr Trump wrote.
He slammed Mr Cruz for issuing a statement from Iowa saying that a fellow candidate, retired neurosurgeon Ben Carson, was quitting the race, and for "lying" to voters about Mr Trump's policies.
"Based on the fraud committed by Senator Ted Cruz during the Iowa caucus, either a new election should take place or Cruz results nullified," Mr Trump wrote.
On the campaign trail in New Hampshire, Mr Cruz looked to capitalise on his momentum against the New York billionaire, who leads Republican polls in the Granite State.
"I wake up every day and laugh at the latest thing Donald has tweeted. Because he's losing it," said Mr Cruz. "We need a commander in chief, not a twitterer in chief."
Mr Cruz won 27.7 per cent of the vote in the Republican caucus in Iowa, staking his claim to be the new standard bearer of the right.
Polls put Mr Trump firmly ahead among Republican voters in New Hampshire, but analysts warn that anything less than a win there will further damage his campaign message that he is a winner.
New York political science professor Jeanne Zaino said Mr Trump's outburst was designed to counter the narrative that he lost in Iowa. "That's a huge component of Donald Trump's campaign. He's been campaigning saying he's a winner and all of a sudden he comes out of Iowa a loser," she said.
Meanwhile, two more Republicans have dropped out of the race for the White House, with Kentucky Senator Rand Paul and former Pennsylvania senator Rick Santorum the latest to quit the fast-shrinking field for the party's presidential nod. Both failed to ignite mass voter interest in Iowa, coming fifth and 11th respectively in a field of 12 candidates.
Mr Santorum threw his weight behind Florida Senator Marco Rubio, whose star has risen in recent weeks. Mr Rubio took more than 23 per cent of the vote in Iowa, anointing him as the Republican establishment candidate.
The Republican field is now left with nine White House hopefuls, including businesswoman Carly Fiorina, who insisted she is committed to the race despite finishing seventh in Iowa.