Sen. Ted Cruz (R-Tex.) suspended his presidential campaign May 3 after suffering a stinging loss in the Indiana primary to Republican presidential front-runner Donald Trump. (Reuters)

Businessman and reality-TV star Donald Trump became the Republican party’s presumptive presidential nominee on Tuesday night, after Trump’s closest rival – Sen. Ted Cruz (R-Tex.) – withdrew from the race, following a crushing victory by Trump in the Indiana primary.

The GOP’s chairman, Reince Priebus, called Trump the “presumtive [sic] GOP nominee” in a Twitter message about 9 p.m., and added a plea that “we all need to unite and focus on defeating” Democratic front-runner Hillary Clinton.

In the Democratic race in Indiana, Sen. Bernie Sanders (Vt.) was projected as the winner, taking an upset victory over Clinton. That victory will not allow Sanders to make up much ground in the race for Democratic delegates, but it will ensure that their race continues on -- creating a scenario few would have seen coming last summer, with Trump gaining a head start on the Democratic nominee.

In a speech at Trump Tower in New York, Trump promised to win big in November.

“We’re going after Hillary Clinton. She will not be a great president. She will not be a good president. She will be a poor president,” Trump said in his speech, then turning to an attack on a trade deal, NAFTA, signed by Clinton’s husband. Trump then repeated a previous promise to stop American companies from shifting jobs overseas.

Trump turned gracious toward Cruz, whom he had excoriated as “Lyin’ Ted” and “wacko” as recently as two and a half hours before.

“Ted Cruz, I don’t know if he likes me, or if he doesn’t like me, but he is one hell of a competitor,” Trump said. “He is a tough, smart guy. And he has got an amazing future.”

Trump does have one remaining GOP challenger: Ohio Gov. John Kasich. Kasich is now last holdout from a field of 16 that once included some of the GOP’s brightest lights: four governors, four senators, and a massively well-funded member of the Bush dynasty.

On Tuesday, Kasich vowed to remain in the race. But his hopes are vanishingly small: he has won just a single state – his own – and still has fewer delegates than long-gone candidate Marco Rubio (Fla.).

“We’re re-energized,” Kasich’s top strategist, John Weaver, said on Tuesday night. “We’re not quitting until someone has 1,237 delegates,” he said, which is the number needed to clinch the GOP nomination. With Cruz out of the race, Trump seems very likely to get that number – and more – in the primaries to come.

Cruz withdrew in a speech in Indianapolis, after being defeated by 16 points in a state where he had pinned all this campaign’s remaining hopes.

Republican presidential candidate Donald Trump held a campaign event at Trump Tower in Manhattan, after sweeping the Indiana primary. (Victoria Walker/The Washington Post)

“I’ve said that I would continue on as long as there is a viable path to victory. Tonight, I’m sorry to say it appears that path has been foreclosed,” Cruz said. “We gave it everything we’ve got. But the voters chose another path. And so with a heavy heart – but with boundless optimism, for the long-term future of our nation – we are suspending our campaign.”

In New York City, a group of Trump’s longest-serving campaign staffers stood quietly and watched a television in Trump Tower, waiting for the candidate to speak. Many had their arms crossed or hands folded and they displayed little emotion, as dozens of cameras were trained on them. There were a few whispered comments and Trump campaign manager Cory Lewandowski kept his eyes glued to his phone screen.

When Cruz said the words that made the news formal, the lobby burst into cheers. As Cruz said that the voters had chosen a path, a woman yelled: “Yeeees!”

The Trump campaign staff remained quiet, so as not to be caught celebrating a rival’s ultimate downfall. Two aides clapped. Lewandowski looked up from his phone and stared at the television, his eyes glistening. As the speech ended, Lewandowski and a few other top aides embraced one another in a group hug that quickly became tighter and tighter.

Cruz’s announcement ends his own unlikely political journey: outside of Trump, few politicians have ever risen as fast in the recent history of the GOP. As recently as 2012, he was a long-shot challenger in a Texas senate race. Cruz won, and quickly became famous outside Washington – and loathed within it – for leading an ill-fated effort to stop President Obama’s health-care law, which led to a government shutdown in 2013.

Cruz used his popularity among the GOP base to become a top challenger in this race – but his outsider candidacy was defeated by an even more famous, more transgressive Republican outsider: Donald Trump.

In this race, Cruz proved unable to expand his appeal outside of his party’s most conservative, and most evangelical sections. He had expected that support to be a floor. Instead – with Trump sweeping away the party’s other factions – it was Cruz’s ceiling.

The only Republican left to challenge Trump now is Ohio Gov. John Kasich, who has no hope of catching Trump in the race for GOP delegates: even after Indiana, Kasich remains in fourth place in the delegate count, trailing long-gone Rubio. Cruz’s withdrawal makes it very likely that Trump will win the 1,237 delegates he needs to lock up the GOP nomination, and avoid a contested convention.

Cruz desperately needed a victory in Indiana, both to deny Trump delegates and to prove he could beat the front-runner one-on-one. Even after days of desperate campaigning, Cruz saw this state slip away.

In fact, Cruz’s furious efforts seemed to backfire: in Indiana, it was Trump stealing away Cruz’s traditional supporters, not the other way around. Trump led the Texas senator by a narrow margin among evangelicals, and among college graduates — two groups that had broken for Cruz in the past, according to preliminary exit polls reported by CNN.

Trump also racked up big wins, as usual, among the non-evangelical, and among those without college degrees, according to the polls reported by CNN.

For Trump, the victory adds to an incredible political story. When he entered the race, last summer, Trump was such a long-shot that his campaign had to recruit tourists off the street to fill out his crowd, handing them t-shirts and pre-written signs. But he quickly took the lead, drawing on voters’ resentment of illegal immigration and of manufacturing jobs shipped overseas.

Along the way, the braggadocious mogul knocked off Jeb Bush, the scion of a Republican dynasty; Rand Paul, the heir to Ron Paul’s liberty movement; Rubio, the face of his party’s future; plus four governors and famed neurosurgeon Ben Carson. He broke the rules of American politics: insulting his opponents’ looks, repeating conspiracy theories (on Tuesday, Trump repeated a report that Cruz’s father had a connection to John F. Kennedy’s assassin), and once bragging about the size of his genitals in a televised debate.

But Trump’s style, substance and business resume resonated with voters, and he benefited from rivals who took Trump lightly, and blasted each other until it was too late.

Now, it seems more likely than ever that Trump will be the star of the 2016 GOP convention, and the first political neophyte to be a major-party nominee since Dwight Eisenhower in 1952.

Even after the Republican race was called, one leader of the “#NeverTrump” movement vowed to fight on until the race was clinched.

“We continue to give voice to the belief of so many Republicans that Trump is not a conservative, does not represent the values of the Republican Party, cannot beat Hillary Clinton, and is simply unfit to be President of the United States,” said Katie Packer of the anti-Trump Our Principles PAC in an emailed statement.

Ohio Gov. Kasich had less than 10 percent of the vote in the GOP race. Kasich had conducted an odd race in Indiana: he first reportedly agreed to not campaign there, so Cruz could face Trump one-on-one, but then said that supporters should still vote for him.

On Tuesday night, Kasich’s campaign issued a memo that said Kasich would vowed to stay in the race until Trump reaches 1,237 delegates.

“Our strategy has been and continues to be one that involves winning the nomination at an open convention,” Kasich’s chief strategist, John Weaver, said in the memo. Kasich has won so few delegates that — for weeks -- it has mathematically impossible for him to reach 1,237 himself.

In interviews with Indiana Republican voters on Tuesday, many said they supported Trump because they believed only a businessman could truly change the way government does business.

“He’s the only candidate who is really going to change the system. Everyone else is in bed with the Republican leadership,” said Justin Stinson, 48, a Bloomington software engineer who voted for Trump at a precinct near Indiana University.

In the Democratic race, Sanders’s good showing was built on strong support from young voters – he won those under 30 by more than 40 points. Sanders also led Clinton among voters ages 30-44 by about 30 points, an improvement among his showing in earlier states. Clinton won voters ages 45-64 by an 8-point margin, and seniors by 20 points, according to preliminary exit polling reported by CNN.

Sanders also led Clinton by a larger-than-usual margin – more than 20 points -- among white Democrats, CNN reported.

At a large precinct in Bloomington, 42-year-old Anita Sumner said she voted for Sanders in the Democratic race because of his positions on income inequality and other issues.

“I’m not just going to vote for someone who has a realistic chance of winning,” said Sumner, a receptionist for a Bloomington financial company.

But Sumner, like another Sanders backer, Indiana University staffer Kathy Wyss, said she would not hesitate to back Clinton if she became the Democratic nominee.

In the smaller town of Rising Sun, Pamela Rees, a 54-year-old physicist, voted for Clinton. “I was tempted by Bernie,” she said, “but I’m an economics wonk, and Bernie never released anything of real depth. Hillary’s not going to be perfect, but she knows how to get in there and achieve things.”

Sanders took the stage at his rally in Louisville when less than 10 percent of the vote was in across the river in Indiana. There were no obvious signs of the election, no screens showing results, and for a while, no reference to the election.

Shortly before 8 p.m., a cheer went up as some supporters got cell service and saw Sanders moving ahead in Indiana.

“Hold off,” he said, “I think we don’t know for sure.”

With Clinton far ahead in the delegate count, a Sanders win here is unlikely to affect the ultimate outcome of the nomination. Clinton spent the day in West Virginia and Ohio, turning her focus to the general election.

For Cruz, the last days of the race in Indiana were a painful demonstration that his time and momentum were running out.

Cruz had sought to draw the party’s establishment behind him. But, given his prickly history, that was a hard sell. Cruz was denounced by former House speaker John A. Boehner (R-Ohio) — whom Cruz had tormented by stirring up House conservatives to oppose their leader — as “Lucifer in the flesh.”

And, as Cruz sought to draw the party’s red-meat wing away from Trump, he was beset by hecklers, rumors and bad luck. Fiorina fell off a campaign stage. Trump supporters shouted out in his rallies.

And, then, on Tuesday, Cruz was all the way through the looking glass. On television, Trump cast Cruz as a tool of the establishment, and a man who “makes stuff up.”

In the same interview, Trump attacked Cruz by referring to a report in the National Enquirer: that Cruz’s father Rafael had been connected to the assassin of John F. Kennedy.

“His father was with Lee Harvey Oswald prior to Oswald being, you know, shot,” Trump said during a telephone interview with Fox News. “I mean the whole thing is ridiculous. What is this? Right? Prior to his being shot. And nobody even brings it up. I mean, they don’t even talk about that — that was reported. And nobody talks about it.”

Trump seemed to be talking about a photo published last month by the National Enquirer that shows Oswald and another man distributing pro-Castro leaflets in New Orleans in 1963. The tabloid claims that the second man is Rafael Cruz, the senator’s Cuban-born father, an explosive accusation that has not been corroborated.

Indiana had been Cruz’s last best chance. He spent his last day there responding to questions about whether his father was a crony of Lee Harvey Oswald.

“The National Enquirer is tabloid trash,” said Cruz. “It was a couple of weeks ago that the National Enquirer wrote this idiotic story about JFK, and Donald was dismayed that the mainstream media wasn’t repeating this latest idiocy, so he figured he had to do it himself.”

“I will say this: This morning, Donald Trump went on national television and attacked my father. Donald Trump alleges that my dad was involved in assassinating JFK. Now let’s be clear, this is nuts. This is not a reasonable position,” he said.

Cruz sarcastically said his dad killed Kennedy. “He is secretly Elvis and Jimmy Hoffa is buried in his back yard,” he added.

Johnson reported from South Bend. Fahrenthold, Juliet Eilperin and Anne Gearan reported from Washington. Sean Sullivan from Indianapolis and Barb Berggoetz from Bloomington contributed to this report.