In their latest presidential debate, the Republican contenders clashed over illegal immigration and the war in Iraq. From Washington, VOA National Correspondent Jim Malone has the latest on the race for the Republican Party's presidential nomination.

Illegal immigration is an emotional issue for many Republican voters. With that in mind, some of the top Republican White House contenders exchanged pointed barbs over who would be tougher against the flow of illegal immigrants across the U.S. border with Mexico.

During the debate sponsored by YouTube and CNN, former Massachusetts Governor Mitt Romney accused Republican frontrunner Rudy Giuliani of being too welcoming to illegal immigrants during his time as mayor of New York City.

"The mayor said, and I quote almost verbatim, which is if you happen to be in the country in an undocumented status, and that means you are here illegally, then we welcome you here," he said.

Giuliani is known for striking back at critics, and did just that with Romney.

GIUILIANI: "There is even a sanctuary mansion. At his [Romney's] own home, illegal immigrants were being employed. If you are going to take a holier-than-thou attitude that you are perfect on immigration..."

ROMNEY: "I am not perfect."

GIULIANI: "It just so happens that you have a special immigration problem that nobody else up here has. You were employing illegal immigrants."

Illegal immigration has become a key issue in the Republican presidential caucuses and primaries that begin in Iowa on January 3.

The Republican contenders also debated Iraq.

Former Senator Fred Thompson of Tennessee was asked by a YouTube questioner how long U.S. troops should remain in Iraq.

"We should not be there any longer than necessary, and we do not know how long that will be," he said. "But we should be there absolutely as long as it takes to complete our mission there."

Texas Congressman Ron Paul remains the only Republican presidential contender who supports an immediate withdrawal from Iraq.

"The best commitment we can make to the Iraqi people is to give them their country back," he said. "That is the most important thing we can do."

Paul's answer drew a response from Senator John McCain of Arizona, who noted an improved security situation in Iraq as a result of the U.S. troop surge.

"I just finished having Thanksgiving with the troops, and their message to you is, 'Let us win, let us win,'" he said.  

Previous Republican debates featured attacks from several of the candidates on Senator Hillary Clinton, the frontrunner for the Democratic Party's presidential nomination.

There were fewer jabs at Clinton in this debate, though former Arkansas Governor Mike Huckabee did manage to work in her name in an answer to a question about future space exploration.

"Whether we need to send somebody to Mars, I do not know. But I will you tell what. If we do, I have got a few suggestions, and maybe Hillary [Clinton] could be on the first rocket to Mars," he said.

Huckabee appears to be on the move in the latest poll in the early contest state of Iowa. A new survey by the Rasmussen Reports shows Huckabee vaulting into a narrow lead in Iowa over Romney, who retains the lead in the early voting state of New Hampshire, while Giuliani continues to lead the Republican field in national polls.