By SCOTT BAUER, Associated Press

AIKEN, S.C. (AP) — Donald Trump and Texas Sen. Ted Cruz continued to joust for primacy heading into the South Carolina primary next weekend, foregoing policy differences for name-calling and insults.

Trump called Cruz "nuts," "dishonest" and "an unstable person," while Cruz questioned both Trump's conservative credentials and whether he had the temperament to be president. Cruz is trying to weaken Trump's standing among South Carolina's social conservatives and evangelical Christians, a key voting bloc in Saturday's contest.

"The people of South Carolina want a consistent conservative they can trust," Cruz told reporters before his rally in Aiken. He also released a new television ad attacking Trump, showing footage of his praising Planned Parenthood and Hillary Clinton. It ends with the line, "South Carolina cannot trust Donald Trump."

Trump threatened to sue Cruz, challenging his eligibility to serve in the White House unless he stops airing what Trump calls "false ads" and retracts what the billionaire real estate mogul called a series of lies.

Trump called Cruz "the most dishonest guy I think I've ever met in politics."

"I think he's an unstable person," he said, later declaring: "He's nuts."

Speaking to hundreds of supporters, Cruz said he intends to make the presidential race a referendum on the Supreme Court and the importance of electing a president who will nominate conservatives. The issue is at the forefront of the presidential race following the sudden death of conservative Justice Antonin Scalia, whom Cruz praised as a "lion of the law."

Cruz said before his rally that a vote for Trump would be a vote for doing away with Second Amendment gun rights, predicting that the billionaire businessman would appoint liberal justices to the Supreme Court. He ticked off a list of Democrats Trump had donated to in the past, including 2004 presidential nominee John Kerry.

Cruz also blasted Trump's sister, a federal appellate judge, calling her a "radical pro-abortion extremist" who should not be considered for the Supreme Court vacancy.

Trump's sister, Maryanne Trump Barry, is a judge on the 3rd U.S. Circuit Court of Appeals in Philadelphia. Trump has said she would make a good justice, but Cruz said she would not be a good choice, citing an opinion she wrote in 2000 that held a New Jersey law banning late-term abortions placed an "undue burden" on a woman's constitutional right to have the procedure.

Cruz also took issue with Trump and Florida Sen. Marco Rubio. Both called him a liar during Saturday's debate. Cruz said they both "simply scream 'Liar, liar!'" whenever their records are questioned, and that approach would not work when negotiating with the likes of Russian President Vladimir Putin.

Cruz also blasted Trump's apparent confusion during a Republican debate last year over what constituted the nuclear triad as an example of how the real estate mogul is unprepared to be president. And Cruz again returned to criticizing Trump's praise of Planned Parenthood.

Cruz released a television ad on Sunday attacking Trump for previously saying Planned Parenthood "serves a good function." In Saturday's debate Trump said that the organization "does do wonderful things, but not as it relates to abortion."

"He's entitled to have that opinion," Cruz said Monday. "A lot of liberal Democrats have that opinion."

Cruz also said Rubio's positions on supporting a path to citizenship puts him in line with "a lot of liberal Democrats" including Hillary Clinton. Rubio has previously supported a path to citizenship for people in the country illegally, but has backed off that position and now says border security must be increased first.

Even as Cruz sharpened his attacks on Rubio and Trump, he said the campaign "shouldn't just be about insults and personal attacks."

___

Associated Press writer Jill Colvin in Mount Pleasant, South Carolina, contributed to this report.