Trump lashed out at Rubio by attacking him for his "meltdown" in the debate in early February saying, "I watched him repeat himself five times four weeks ago."
"I just watched you repeat yourself five times five seconds ago," Rubio contended.
Although the exchange between Rubio and Trump went on even further, Trump was never able to give clear details beyond eliminating state lines, even though moderator Dana Bash also asked him to provide more detail.
Cruz also attacked Trump on his stance on health care by claiming that Trump previously advocated for "socialized medicine," a claim Trump sharply refuted.
Cruz then questioned Trump if he had ever said he was for the government paying for everyone's health care, implying that Trump had touted the single-payer health care systems in Canada and Scotland in previous debates.
Later in the debate, Cruz argued that if Trump were to win the GOP nomination, he would have no chance at beating Democratic frontrunner Hillary Clinton because he would not be able to attack her on the basis of her corruption as Secretary of State.
"You know, the mainstream media is laying off Donald now. They're going to pick apart his taxes. They're going to pick apart his business deals. And let's take, for example, one of Hillary's great vulnerabilities, the corruption at the Clinton Foundation, the fact that she had CEOs and foreign companies giving her money while she was secretary of state," Cruz said. "The next Republican nominee needs to be able to make that case against Hillary. And if Donald tried to do it, Hillary would turn to Donald and say, 'but gosh, Donald, you gave $100,000 to the Clinton foundation. I even went to your wedding.'"
"He can't prosecute the case against Hillary, and we can't risk another four years of these failed Obama policies by nominating someone who loses to Hillary Clinton in November," Cruz added.
Trump's reasoning for not releasing his tax returns to the public is because he is being audited by the IRS. However, Cruz argued that Trump could still release his tax returns to the public despite the audit, unless there was something he didn't want the public to see.
"If there's nothing, release them tomorrow," Cruz said. "They're already prepared. The only reason he's not releasing them … is because he's afraid that he will get hit."
Cruz also mentioned the fraud lawsuit against Trump University, which is scheduled to be heard in July.
"I want you to think about, if this man is the nominee, having the Republican nominee on the stand in court, being cross-examined about whether he committed fraud," Cruz explained. "You don't think the mainstream media will go crazy on that?"
"And on substance, how do we nominate a candidate who has said Hillary Clinton was the best secretary of state of modern times, who agreed with her on foreign policy, who agrees with Bernie Sanders on health care, who agreed with Barack Obama on the Wall Street bailout?" Cruz asked. "We've got to win this election and we can't do it with a candidate who agrees with Hillary Clinton and can't take it to her and beat her on the debate stage and at the polls."