INDIANAPOLIS — (CNN)  Donald Trump is the presumptive Republican presidential nominee following a decisive victory in the Indiana primary and the decision by Ted Cruz to drop out of the race.

Though Trump has not formally secured the 1,237 delegates he needs to win the nomination — and likely won’t until June — there is no serious opposition left to block his path.

His victory amounts to a stunning takeover of the Republican Party by a candidate with no political experience. Along the way, he eviscerated the GOP’s most accomplished presidential field in a generation and captured the Zeitgeist of a party in which grass roots voters harbor deep ill will toward establishment elites.

“It is a beautiful thing to watch, and a beautiful thing to behold,” Trump said during a victory speech. “We are going to make America great again.”

Cruz tried everything to pull off a last-ditch win in Indiana, including the unusual move of selecting Carly Fiorina as his running mate even though he wasn’t the nominee. He also forged a pact with John Kasich that would allow him to focus on Indiana while the Ohio governor would devote his time to later states.

But none of the moves worked.

“We left it all on the field in Indiana. We gave it everything we’ve got but the voters chose another path,” Cruz said. “So with a heavy heart but with boundless optimism for the long-term future of our nation, we are suspending our campaign.”

Following Cruz’s speech, Republican National Committee Chairman Reince Priebus tweeted Trump is now the presumptive nominee and encouraged the party to “unite and focus on defeating” Hillary Clinton.

Trump paid tribute to Cruz in an effort to bring the party together.

“He is one tough competitor,” Trump said. “He is a smart tough guy.”

Cruz, facing the prospect of an Indiana defeat, snapped after weeks of personal attacks from Trump that included fresh insinuations that his father was associated with Lee Harvey Oswald.

“I’m going to tell you what I really think of Donald Trump,” he told reporters at a morning news conference.

Cruz blasted Trump as a “pathological liar,” “utterly amoral,” “a narcissist at a level I don’t think this country’s ever seen” and “a serial philanderer.”

He unleashed his full arsenal of insults in his attack on Trump.

“He is proud of being a serial philanderer … he describes his own battles with venereal diseases as his own personal Vietnam,” Cruz said, citing a decades-old Trump appearance on “The Howard Stern Show.”

“This man is a pathological liar, he doesn’t know the difference between truth and lies … in a pattern that is straight out of a psychology textbook, he accuses everyone of lying,” Cruz said as Indiana voters headed to cast their ballots. “Whatever lie he’s telling, at that minute he believes it … the man is utterly immoral,” Cruz said.

Trump hit back in a statement blasting Cruz as a “desperate candidate trying to save his failing campaign.”

The volley reflected the increasingly personal battle between Cruz and Trump in the final days of the Indiana contest. Earlier Tuesday, Trump had criticized Rafael Cruz, the senator’s father, calling him “disgraceful” after he urged evangelical voters in Indiana to reject his son’s rival.

Trump also referenced a report from the tabloid National Enquirer — without naming the publication — which alleged that it had identified Rafael Cruz in a photo with Lee Harvey Oswald months prior to the JFK assassination. CNN has not independently confirmed that report — and there is no evidence that it is true.

“And (Ted Cruz’s) father, you know, was with Lee Harvey Oswald prior to Oswald’s, you know, being shot. I mean the whole thing is ridiculous,” Trump said in an interview on “Fox and Friends.” “I mean what was he doing with Lee Harvey Oswald, shortly before the death? Before the shooting? It’s horrible.”

Trump quickly turned his fire on Clinton, saying she would be a “poor president.” He also said she “doesn’t understand trade” and lashed out at the “deep carnage” he said had been wrought by the North American Free Trade Agreement that was ratified during the presidency of her husband, Bill Clinton.

Trump’s candidacy has galvanized the GOP, bringing in voters — especially in regions like the Rust Belt — that might not otherwise be attracted to the party’s message. In the process, he’s toppled a GOP field that, at the start, included many well-respected governors and senators.

For his part, Kasich insisted he would remain in the race.

“Tonight’s results are not going to alter Gov. Kasich’s campaign plans,” said John Weaver, Kasich’s chief strategist. “Our strategy has been and continues to be one that involves winning the nomination at an open convention.”

Sanders wins Indiana

Meanwhile, Bernie Sanders will win the Indiana Democratic primary, according to a CNN projection. That victory could help boost his campaign’s morale but is unlikely to cut deeply into Clinton’s large delegate lead that has her on track for the nomination.

The painful state of the race for Sanders means that his only hope of winning the nomination would be to persuade Democratic superdelegates at the convention to abandon the former secretary of state — an unlikely scenario considering that group is largely made up of party insiders long aligned with Clinton.

That is one reason why the Clinton campaign has begun stressing that it is time to unite the party and concentrate on the race against Republicans in the fall.

But Sanders made clear Tuesday he would challenge Clinton during all the remaining primaries and called on her to agree on a date for a debate in California, which holds its primary on June 7.

“The Clinton campaign thinks this campaign is over,” Sanders said in a statement. “They’re wrong. Maybe it’s over for the insiders and the party establishment, but the voters in Indiana had a different idea.”

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