Cruz announced late Tuesday that he no longer had a viable route to victory, amid cries of shock and disappointment from supporters.

"From the beginning, I've said that I would continue on as long as there was a viable path to victory. Tonight, I'm sorry to say, it appears that path has been foreclosed," the Texas senator told the crowd in Indianapolis.

"We gave it everything we've got, but the voters chose another path," said Cruz, whose exit leaves the outsider John Kasich as Trump's sole challenger.

Trump was on track to take well over 50 percent of the vote in Indiana, US broadcasters had announced earlier on Tuesday, bringing him much closer to outright victory in the race to be the party's candidate for the White House.

Cruz had been counting on a win in Indiana's primary to slow the New York billionaire's progress toward the Republican nomination.

But polls in recent days showed Trump opening up a substantial lead in the Midwestern state over the Texas senator, whose brand of Christian conservatism had been expected to have wide appeal.

Based on 13 percent of precincts reporting, the billionaire took 53.8 percent of the vote, streets ahead of Cruz on 33.9 and Ohio Governor John Kasich on 9.4 percent.

Shortly after Cruz's exit, Reince Preibus, the chairman of the Republican Party declared Trump the presumptive nominee, despite his candidacy deeply dividing the party in recent months.

Trump strides ahead

Cruz's suspension firmly sets Trump on the path to the Republican nomination, as although, Ohio Governor John Kasich remains in the race, he has barely one-tenth of Trump's support, and analysts say it will be difficult for him to catch up.

To win the nomination, Trump needs support from 1,237 Republican delegates and has currently amassed 1,002 names, according to CNN's tally. While Cruz had won 572 delegates, Kasich trails with 156.

But the New York billionaire could still be denied the nomination at the party's Convention, which runs from July 18 to 21 in Cleveland, Ohio.

Rivalry intensifies

Ahead of Tuesday's vote, the attacks between the two rivals grew noticeably more personal. In a Fox News interview, Trump linked Cruz's father to the murderer of John F. Kennedy, causing the Texas senator to fire back by calling Trump a "moron," among other things.

"We are not a proud, boastful, self-centered, mean-spirited, hateful, bullying nation," Cruz said alongside his wife Heidi and running mate Carly Fiorina earlier in the day. "If Indiana does not act, this country could well plunge into the abyss."

Trump had his own words for Cruz, however. In a statement released following the senator's most recent comments, Trump said Cruz was "a desperate candidate trying to save his failing campaign."

"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."

Cruz also faced criticism for his choice of running mate, businesswoman Carly Fiorina.

Democratic race tight

The Democratic race saw Bernie Sanders beat Hillary Clinton in the same Midwestern state, according to a projection by The Associated Press.

The self-declared democratic socialist, was ahead of Clinton by 53.2 percent to 46.8 percent with about three quarters of precincts reporting, although Clinton remained well ahead in the delegate battle for the nomination.

mm/rc (AFP, Reuters)