CNN's Jake Tapper refuted Donald TrumpDonald John TrumpDem lawmaker says Electoral College was 'conceived' as way to perpetuate slavery Stanley Cup champion Washington Capitals to visit White House on Monday Transportation Dept requests formal audit of Boeing 737 Max certification MORE's recent allegations that Ted CruzRafael (Ted) Edward CruzO'Rourke: Decisions on late-term abortions 'best left to a woman and her doctor' New report details O'Rourke's prankish past O'Rourke sees 'a lot of wisdom' in abolishing Electoral College MORE's father is linked to John F. Kennedy assassin Lee Harvey Oswald, calling the claim ridiculous and shameful.

"Every time you think this race cannot get any more ludicrous, it does," Tapper said on "The Lead," calling the exchange between the two GOP presidenetial rivals Tuesday "bitter and stunning."

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Trump said Tuesday morning that Cruz's father was with Oswald before he shot Kennedy, referencing a National Enquirer story that published images of what it said was Rafael Cruz and Oswald passing out pro-Fidel Castro leaflets in 1963 in New Orleans, a few months before the JFK assassination.

Tapper called the report "bizarre" and "completely uncorroborated."

"And I use the term 'report' loosely," he said.

Tapper said the tabloid, which endorsed Trump and is run by a friend of the business mogul's, has been running "smear after smear against Cruz and his family."

He said there is no proof that the photo featured in the tabloid is Cruz's father, and the Cruz campaign has denied it.

When Trump called into "Fox and Friends" on Tuesday morning, he took issue with the fact the nobody had been talking about the link between Cruz's father and Oswald. Tapper tried to make it clear that it isn't talked about because it isn't true.

"I cannot believe I need to say the following but here goes," Tapper said Tuesday. "There is no corroborated evidence that Ted Cruz's father ever met Lee Harvey Oswald or, for that matter, any other presidential assassin. We in the media don't talk about it because there's no evidence of it."

On the other hand, before the picture was taken, Tapper said, Rafael Cruz's sister was "brutally beaten by Castro forces and Rafael Cruz had denounced the regime. So any suggestion that Cruz's father played a role in the Kennedy assassination is ridiculous and frankly shameful," he said.

"That's not an anti-Trump position or a pro-Cruz position, it's a pro-truth position."

On Tuesday, Cruz shot back against Trump after the front-runner made the claims, calling Trump "utterly amoral" and a "pathological liar."