 -- As many political friendships are wont to do, the once-public bromance between Donald Trump and Sen. Ted Cruz is officially, completely, unequivocally dead.

Let’s mark the date of its utter demise as Tuesday, the day of the Indiana primary, when each one slung mud in a spectacularly scurrilous fashion: Trump accusing Cruz’s father of having ties to John F. Kennedy assassin Lee Harvey Oswald (with no proof); and Cruz responding in turn by referencing Trump radio interviews from the 1990s in which the businessman joked that avoiding sexual diseases in the 1980s was like his “personal Vietnam.”

It all began in the morning, as Indiana voters headed to the polls.

It All Started With Ted Cruz's Father

Trump was discussing the elder Cruz’s pitch to evangelicals with the hosts of “Fox and Friends.” Rafael Cruz has exhorted Christians to vote for his son, to avoid what he said would lead to the destruction of the country if Trump becomes president. Trump called his efforts “disgraceful."

"It's disgraceful that his father can go out and do that. And just – and so many people are angry about it,” Trump said. “And the evangelicals are angry about it, the way he does that. And you know, there's a whole thing and, you know, his father was with Lee Harvey Oswald prior to Oswald's being -- you know, shot.

“I mean, the whole thing is ridiculous. What is this, right prior to his being shot, and nobody brings it up. They don't even talk about that,” Trump said on Fox.

He added, "I mean, what was he doing with Lee Harvey Oswald shortly before the death, before the shooting? It's horrible.”

'This Is Nuts'

Cruz then responded while speaking to reporters in Evansville, Indiana.

"I'm going to tell you what I really think of Donald Trump. This man is a pathological liar,” Cruz began. He went on to call him “utterly amoral” and a “serial philanderer.”

He also said: "Donald Trump alleges that my dad was involved in assassinating JFK. Now, let's be clear. This is nuts."

And then he delivered the final stab.

"This is not a secret, he’s proud of being a serial philanderer. … The [would-be] president of the United States talks about how great it is to commit adultery, how proud he is, describes his battles with venereal disease as his own personal Vietnam. That's a quote, by the way, on ‘The Howard Stern Show.’ Do you want to spend the next five years with your kids bragging about infidelity?” Cruz asked.

Dusting Off a Howard Stern Interview

He was referring to a interviews during the 1990s on “The Howard Stern Show” uncovered by Buzzfeed News.

“You know, if you’re young, and in this era, and if you have any guilt about not having gone to Vietnam. We have our own Vietnam. It’s called the dating game,” Trump said in 1993 during a discussion of his well-publicized germaphobia and the ongoing AIDs epidemic at the time.

Trump added in 1997: “It is a dangerous world out there — it’s scary, like Vietnam. Sort of like the Vietnam era. It is my personal Vietnam. I feel like a great and very brave soldier.”

Trump responded to Cruz’s comments in a statement today, calling him a "desperate candidate trying to save his failing campaign.”

The statement added, "Over the last week, I have watched Lyin’ Ted become more and more unhinged…Today’s ridiculous outburst only proves what I have been saying for a long time, that Ted Cruz does not have the temperament to be President of the United States."

Once 'Terrific,' Now 'Detached From Reality'

The two began this political cycle speaking almost glowingly of each other: Cruz praised his rival, tweeting that Trump was “terrific” and calling the pair friends. Trump, for his part, has called Cruz a “special guy.”

But as the race grew tighter, the friendship flamed, culminating in the all-out war that followed Trump’s retweeting an unflattering picture of Cruz’s wife Heidi, and suggesting that Cruz’s father had a connection to Oswald.

Trump’s claims are completely unsubstantiated, and appear to be a reference to a tabloid article published by the National Enquirer two weeks ago that claimed to have photographic evidence that Cruz passed out pro-Castro leaflets with Kennedy’s assassin, Lee Harvey Oswald, in 1963 in New Orleans.

The Cruz campaign told ABC News today in a statement, "Trump is detached from reality, and his false, cheap, meaningless comments every day indicate his desperation to get attention and willingness to say anything to do so," adding, "It's a garbage claim - let Donald talk about garbage, Ted will talk about jobs, freedom and security for the American people."

The elder Cruz was born in Cuba and, for a time, supported Castro, even after his emigration to the United States, fighting against the Fulgencio Batista regime in the 1950s. As part of the anti-Batista underground, Rafael Cruz was jailed and tortured.

Cruz has since denounced Castro.