Donald Trump
Republican presidential candidate Donald Trump speaks to the crowd at town hall meeting Saturday, December 12, 2015 in Aiken, South Carolina. The South Carolina Republican primary is scheduled for February 20, 2016.Sean Rayford/Getty Images

Republican presidential candidates Donald Trump and Ted Cruz appear to have called off a campaign truce with the two exchanging not so friendly comments about each other, days before the fifth GOP debate. Trump called Cruz "a little bit of a maniac" as it's revealed that the Texas senator has soared to the lead in Iowa.

Trump's comments, made to CNN and Fox News, come after recordings of Cruz reveal him questioning the judgement of the real estate mogul. "I was against going into Iraq. That's good judgement," Trump told CNN's Jake Tapper. "I was for bombing (the Islamic State's) oil long before anyone else was talking about it. That's good judgement. I have great judgment. I would say I have far better judgement than Ted."

The bombastic frontrunner, who has come under fire following comments he made about Muslims, said that the cordial relationship between them "will come to an end pretty soon". In a separate interview with Fox News Sunday, Trump was true to his word and questioned Cruz's work in the US Senate. "You look like the way he's dealt with the Senate, where he goes in there like—frankly like a little bit of a maniac. You're never going to get things done that way," he said.

Trump continued, "You can't walk into the Senate and scream and call people liars and not be able to cajole and get along with people. He'll never be able to get anything done, and that's the problem with Ted." CNN noted that the barbs between the two is likely to intensify as they vie for the top spot in Iowa—a key primary state.

Just seven weeks before the Iowa caucuses, Cruz soared to first place, beating out Trump by double digits. A recently Des Moines Register poll revealed Cruz clinched top spot with 31% to Trump's 21%. Trump wasted no time in attacking the poll, claiming it was biased against him in a tweet promoting a 7 December CNN Iowa poll, which declared him the winner, 33% to Cruz's 20%.

The two will face off in the fifth Republican debate, sponsored by CNN, on 15 December in Las Vegas. Cruz has been closing the gap between himself and Trump in recent national election polls. A NBC/Wall Street Journal poll released on 13 December revealed Trump only had a five percentage point lead over Cruz, 27% to 22%. The two were followed by Marco Rubio (15%), Ben Carson (11%) and Jeb Bush (7%).