The fight for South Carolina is heating up in the Republican presidential race as the top GOP contenders trade insults and jabs just days before the state's primary on Feb. 20.

The Fight for South Carolina

The top GOP contenders are engaged in an all-out war in the lead up to Saturday's Republican primary in the Palmetto State. According to a CNN/ORC poll released Tuesday, Donald Trump has a strong lead in the race with 38 percent, followed by Ted Cruz at 22 percent, Marco Rubio at 14 percent and Jeb Bush with 10 percent.

Despite his lead, Trump has unleashed a barrage of attacks against Cruz, calling him "a liar" for weeks and then describing him as "slimy" and "nasty" at a rally in North Augusta, South Carolina on Tuesday.

The New York real estate mogul has also threatened to sue Cruz for defamation over a campaign ad that shows the businessman saying he is "very pro-choice" during a 1999 interview. The new video, which was released Tuesday afternoon, also accuses Trump of "playing games with the sanctity of life" and being "enthusiastically pro-abortion" for most of his adult life.

Trump fired back, arguing he has evolved on the issue of abortion. Cruz responded to Trump's cease and desist letter by daring him to file the suit.

"I have to say to Mr. Trump you have been threatening frivolous lawsuits for your entire adult life," Cruz said at a press conference on Wednesday. "If you want to file a lawsuit ... file the lawsuit."

Trump, however, is not the only 2016 hopeful branding the Texas senator a liar. Rubio is also taking aim at Cruz, depicting him as a disingenuous politician.

"I've been saying for a while now that Ted unfortunately has proved that he is willing to say or do anything to get elected," said the Florida senator on Wednesday in Mount Pleasant, South Carolina. "What we've seen in the last couple weeks is disturbing"

Cruz responded at a press conference, saying, "Marco Rubio is Donald Trump with a smile."

Despite the attacks, Rubio received a major endorsement from South Carolina Gov. Nikki R. Haley on Tuesday, giving him a boost days before the primary. That announcement came as a blow to Bush, who told reporters Wednesday that he was "disappointed" by Haley's endorsement.

South Carolina: Jeb Bush's Last Stand

While speaking at a campaign event held at a South Carolina country club on Saturday, the former Florida governor bashed Rubio, his former protégé, as unqualified for the position of commander-in-chief.

The audience, however, expressed concern about his campaign. One voter told him he was "afraid your message doesn't resonate" and asked whether Bush was "knocked off center" by Trump's repeated insults.

Throughout the election, Bush has suffered from low poll numbers and a number damaging attacks from Trump. If Bush does not come out in one of the top three spots in South Carolina, his campaign may come to an end.