As the U.S. Presidential campaign heads south, so too has civil discourse.

Republican candidates have resorted to name calling as they jostle for position ahead of Saturday’s primary election in South Carolina.

At last Saturday night’s debate, broadcast on CBS, GOP front-runner Donald J. Trump blasted U.S. Senator Ted Cruz of Texas and former Florida Governor Jeb Bush.

“This is a nasty guy,” Trump said of Cruz. “You are the single biggest liar. You are probably worse than Jeb Bush.”

Bush, a favorite target of Trump’s throughout the campaign, fired back, “I’m sick and tired of him going after my family,” he said.

On Monday, former U.S. President George W. Bush surfaced in support of his little brother, taking a veiled shot at the billionaire businessman.

“These are tough times,” President Bush told an estimated crowd of 3,000 people in North Charleston. “And I understand Americans are angry and frustrated, but we don’t need someone in the Oval Office who mirrors and inflames our angers and frustrations.”

Trump, bolstered by his big victory in the New Hampshire primary, attacked Cruz on Monday, calling the freshman senator “unstable” and a “basket case” and continuing to question whether he is legally qualified to serve as President. Cruz, son of a Cuban father and Canadian mother, was born in Calgary, Alberta, Canada.

“The Democrats are going to bring a lawsuit,” Trump said. “I’m doing him a favor by bringing this up now.”

Meanwhile, U.S. Senator Marco Rubio of Florida is going after the cultural conservative vote in South Carolina. Rubio praised departed U.S. Supreme Court Justice Antonin Scalia for his dissent in the marriage equality case at Saturday’s debate and closed by saying American values are upside down.

“What’s right is wrong and what’s wrong is right,” Rubio said. “We are going to be a country that says a marriage is between one man and one woman.”

Combining the results of six polling firms, Real Clear Politics has Trump leading in the Palmetto State with 36.3 percent support, followed by Cruz (17.8), Rubio (15.8), Ohio Governor John Kasich (9.8), Bush (9.3) and retired neurosurgeon Ben Carson (5.3).

Meanwhile, Democrats are rounding up supporters for Saturday’s caucus in Nevada. On Monday in Reno, Nevada, former Secretary of State Hillary Clinton suggested it was time to doggedly pursue Republican lies.

Recalling an old radio ad from her time in Arkansas in which a dog would automatically bark at lies from politicians, Clinton said it was time to install a canine truth barometer for the GOP.

“We need to get that dog and follow them around and every time they say things like ‘Oh the Great Recession was caused by too much regulation, ‘arh, arh, arh, arh, arh,’” Clinton said, ending with a barking noise that produced laughs from the audience.

Polls have Clinton leading U.S. Senator Bernie Sanders of Vermont in Nevada and also in South Carolina where the Democrats head to next for a closed primary on Feb. 27.