05/03/2016 16:31 EDT | Updated 05/04/2017 01:12 EDT

A weird JFK conspiracy theory from Trump on day he could become de-facto nominee

WASHINGTON — If this is the day Donald Trump becomes his party's presumptive presidential nominee, let the record show that it was of a weirdness befitting the entire race.

On the day of a potentially decisive primary, the front-runner rolled enthusiastically in the mud of an outlandish conspiracy theory: that his rival's dad was somehow linked to John F. Kennedy's assassin.

That drew an understandably outraged response from the rival in question, Sen. Ted Cruz — who has already had his adversary insinuate that his wife is ugly and now that his dad was a old pal of shooter Lee Harvey Oswald.

The mud-flinging front-runner could become unstoppable if he wins Indiana's primary Tuesday.

"This is nuts," an exasperated Cruz told reporters. 

"Yes, my dad killed JFK. He is secretly Elvis. And Jimmy Hoffa's buried in his backyard. ... I'm going to tell you what I really think about Donald Trump: this man is a pathological liar. He doesn't know the difference between truth and lies. He lies, practically every word that comes out of his mouth. ... He combines it with being a narcissist. A narcissist at a level I don't think this country's ever seen ...

"Donald Trump is such a narcissist that Barack Obama looks at him and goes, 'Dude, what's your problem'?"

The trigger for this outburst was Trump's habit of using the platform of a presidential campaign to elevate urban legends into national discussion topics.

He did it recently by recycling a made-up story about a general who supposedly executed Muslims with bullets dipped in pig's blood more than a century ago. He did it again Tuesday by referring to a supermarket-tabloid item about Cruz's father Rafael. It had originally appeared in the National Enquirer — owned by Trump's buddy, David Pecker.

The Miami Herald more recently ran a report questioning the tabloid story — so, naturally, a Trump spokesperson defended the candidate's decision to raise it by saying it had appeared in the Miami Herald.

The original tabloid story was headlined: "Ted Cruz's Father — Caught With JFK Assassin." It said the Cuban-born father was with Oswald a few months before the assassination, at a protest where the latter handed out pro-Castro-Cuba flyers.

Trump brought it up in a TV interview Tuesday.

"His father was with Lee Harvey Oswald prior to Oswald's being — you know, shot. I mean, the whole thing is ridiculous," Trump told Fox News.

"What is this, right prior to his being shot, and nobody even brings it up. They don't even talk about that. ... I mean, what was he doing — what was he doing with Lee Harvey Oswald shortly before the death? Before the shooting? ... It's horrible."

This was after his rival's father — a pastor — described Cruz as God's choice in the campaign: "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," Rafael Cruz said.

For the sake of the Republican party, these now-bitter rivals might have to make sweet pretty soon.

Trump could become unstoppable on his path toward the Republican presidential nomination if he wins today's Indiana primary. Victory would give him a valuable haul of delegates, vastly increasing the likelihood that he will crack the magic number of 1,237 on the final day of primary voting on June 7.

That would allow a first-ballot victory at the summer convention. It would also help him avoid a messy nomination battle over several ballots at the convention.

"Honestly, if we win Indiana, it's over. It's over," Trump told a rally on Monday.

The billionaire said of his rivals: "They're finished."

His rivals wouldn't necessarily be out.

Cruz signalled that he would push the battle to the very end, meaning a batch of primaries on June 7 and then a possible floor fight at the July convention in Cleveland.

"We are in for the distance," he told reporters Monday.

"We're headed to a contested convention."

Alexander Panetta, The Canadian Press