Donald TrumpDonald John TrumpKoch-backed group launches six-figure ad buy against Heitkamp Anti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight MORE on Tuesday slammed "disgraceful" comments from the father of his Republican presidential rival, Texas Sen. Ted CruzRafael (Ted) Edward CruzCruz says Cambridge Analytica assured him its practices were legal Dem battling Cruz in Texas: ‘I can understand how people think this is crazy’ Overnight Tech: Facebook faces crisis over Cambridge Analytica data | Lawmakers demand answers | What to watch for next | Day one of AT&T's merger trial | Self-driving Uber car kills pedestrian MORE, who called on Christians to support his son in the Indiana primary.

“I think it’s a disgrace that he’s allowed to do it. I think it’s a disgrace that he’s allowed to say it,” Trump said during a telephone interview on "Fox and Friends."

Trump touted his support from Jerry Falwell Jr. and other evangelical supporters, saying, "It's disgraceful that his father can go out and do that and so many people are angry about it, and the evangelicals are angry about it, the way he does that."

Rafael Cruz, a minister, was speaking to a group of pastors in Indianapolis on April 25 when he made an appeal on behalf of his son, according to video posted on Facebook.

“I implore — I exhort every member of the body of Christ to vote according to the word of God and vote for the candidate that stands on the word of God and on the Constitution of the United States of America,” Rafael Cruz said in the video clip broadcast by Fox.

“And I am convinced that man is my son, Ted Cruz. The alternative could be the destruction of America," Rafael Cruz added.

Trump and Cruz are battling in Indiana on the day of the state's primary on Tuesday.

During his Fox interview, Trump invoked a tabloid story that claimed to link Rafael Cruz to John F. Kennedy's assassin, Lee Harvey Oswald, which Cruz's campaign last month dismissed as "garbage."

"His father was with Lee Harvey Oswald prior to Oswald being shot. I mean, the whole thing is ridiculous," Trump said. "Nobody even brings it up; they don't even talk about that."

"What was he doing with Lee Harvey Oswald shortly before the shooting?"