By Arun Kumar

Washington, Feb 14 (IANS): The six remaining Republican presidential contenders clashed over issues ranging from immigration to foreign policy, but they all agreed that President Barack Obama should not name a replacement for a dead Supreme Court judge.

One of the most notable exchanges in the Republican debate on CBS News in Greenville, South Carolina ahead of the February 20 South Carolina Republican primary was between frontrunner Donald Trump and Florida governor Jeb Bush.

The brash real estate mogul blasted former president George W. Bush, who will hit the campaign trail in South Carolina on Monday to stump for his brother, calling the Iraq war a "big fat mistake".

Bush hit back saying, "I'm sick and tired of Barack Obama blaming my brother for all of the problems" he faces before quickly turning the fire on Trump.

"While Donald Trump was building a reality TV show, my brother was building a security apparatus" to keep the country safe.

Trump lashed back, saying it was under Bush's watch that the World Trade Centre was attacked on September 11, 2001.

"That's not keeping us safe," he said to loud boos from the audience.

Florida Senator Marco Rubio came to the former president's defence saying, "He kept us safe and I'm forever grateful."

The terrorist attacks of 2001 happened because Bush's predecessor Bill Clinton failed to kill Osama bin Laden when he had the chance, he suggested.

Rubio and Texas Senator Ted Cruz also clashed over their records on immigration reform with Cruz accusing his rival of supporting a "massive amnesty plan" and Rubio charging his Senate colleague with spreading "lies".

Rubio wasn't the only one to call Cruz a liar. Moments later, Trump called the Texas senator "the single biggest liar".

"This guy lied about (retired neurosurgeon) Ben Carson when he took votes away from Ben Carson in Iowa," Trump said, a reference to Cruz allies incorrectly telling voters on the night of the Iowa caucuses that Carson was dropping out of the race.

Trump went on to accuse Cruz of running robo-calls in South Carolina informing voters that Trump was not running in this state.

"This is the same thing he did to Ben Carson. This guy will say anything -- nasty guy," Trump fumed.

Cruz accused Trump of hypocrisy, saying he had called Carson "pathological" and compared the retired neurosurgeon to a child molester.

Looking on at his rivals from the edge of the stage, Carson appeared amused by the vicious attacks and said he had no intention of joining in the mud slinging.

"So many people have said to me, you need to scream and jump up and down like everybody else," Carson said.

But the candidates largely agreed that a successor to Supreme Court justice Antonin Scalia who died earlier Saturday should be nominated by the next president.

Trump said he was certain Obama would make a nomination whether Republicans like it or not and called on Senate Majority Leader Mitch McConnell to slam the brakes.

"It's called delay, delay, delay," he said.