AP Photo/Seth Perlman
Donald Trump.
Multiple outlets projected shortly after polls closed Tuesday that Trump would win the Hoosier State's primary.
"Thank you Indiana!" Trump's account tweeted shortly after he was declared the state's victor.
The GOP frontrunner led in Indiana by more than 20 points over Cruz, a Texas senator, with about 5% of precincts reporting. John Kasich, the Ohio governor, finished a distant third.
The win puts Trump on a glide path to obtain the needed 1,237 delegates necessary to win the nomination.
Late last month, almost all projections forecast that Indiana would be a tough draw for Trump, as well as a must-win, yet favorable, state for Cruz.
The script flipped in the week leading up to the crucial vote, with Trump soaring ahead in the polls while picking up key endorsements such as legendary former Indiana University men's basketball coach Bobby Knight.
A recent NBC/Wall Street Journal poll found that Trump held a gigantic 15-point lead over the Texas senator. FiveThirtyEight gave Trump an 83% chance of winning the state based on its polls-plus model, and a 97% chance of winning based on its polls-only projection.
Trump assured supporters during a Monday rally that his campaign is "way ahead of projection" and that he would secure the Republican presidential nomination on the first ballot at the Republican National Convention in July.
"But if we win Indiana," he added, "it's over."
Knowing that the state, which votes Tuesday, could be the last stand of the "Never Trump" movement, Cruz and anti-Trump forces had gone all out to stop him. Cruz began last week by cutting an unprecedented deal with John Kasich, the Ohio governor.
The deal called for Kasich's campaign to pull out of Indiana, in hopes that his absence would give Cruz the boost he needed to pick up the crucial win. In exchange, Cruz would recede from both Oregon and New Mexico, which both hold contests later in the nominating process.
But less than a week after the deal was announced by both campaigns, the agreement had already collapsed.
The deal wasn't Cruz's only attempt at shifting Hoosier State polls, which showed that Trump held a more than 10-point average advantage leading up to the vote.
Last Wednesday, the Texas senator made another rare announcement. He named ex-presidential hopeful and former Hewlett-Packard CEO Carly Fiorina as his running mate, should he win the GOP nomination. (Both Cruz and Kasich are mathematically eliminated from securing the nomination ahead of the convention, so their potential nominations would have to come from subsequent ballots.)
Trump chastised Cruz for that move as well, calling it a "waste of time."
Based on the results in the state, both moves failed.
Now Trump, who may not have even needed many Indiana delegates, will leave the state with a plethora of them.