With the Republican primary in South Carolina just days away, Ted Cruz has stepped up his fight with Donald Trump, who is threatening to sue him unless he stops airing what the billionaire candidate calls "false ads" and retracts what he called a series of lies.
Cruz questioned both Trump's conservative credentials and whether he had the temperament to be president.
"The people of South Carolina want a consistent conservative they can trust," Cruz told reporters before his rally in Aiken.
Cruz, who is trying to weaken Trump's standing among South Carolina's social conservatives and evangelical Christians, also released a new television ad attacking Trump, showing footage of him praising Planned Parenthood and Hillary Clinton. It ends with the line, "South Carolina cannot trust Donald Trump."
Trump is challenging Cruz’s eligibility to serve in the White House, calling him "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 on Monday, 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."
Hours before the rally Cruz said 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 then pointed at 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."
Based on reporting by the Associated Press.