Nearly half of the state's likely Republican primary voters, 49 percent, said they support Trump, while 34 percent back Texas Sen. Ted Cruz and 13 percent support Ohio Gov. John Kasich.
With less than three days left before Hoosiers go to the polls on Tuesday, Trump's 15-point lead over his nearest rival is the latest sign that the GOP front-runner has a realistic shot at amassing the 1,237 delegates needed to win the nomination outright.
Indiana awards a total of 57 Republican primary delegates, 30 to the winner statewide, and another 27 to the winners of its nine congressional districts. Trump currently has 996 pledged delegates.
It's difficult to overstate the significance of Indiana to the "Stop Trump" movement. Home to large blocs of socially conservative and evangelical Republicans, Indiana is widely seen as the last state in the nominating process where Cruz stands a chance of defeating Trump.
"The entire country is looking to Indiana," Cruz said on NBC's "Meet the Press." "And I think the country is really depending on Indiana to choose the direction of this race."
The new poll also reveals that a last-minute plan hatched by the Cruz and Kasich campaigns to cut into Trump's support may have backfired.
Neither Cruz nor Kasich could possibly win enough delegates in the remaining primary contests to reach the 1,237 delegate threshold to clinch the nomination. But they could prevent Trump from reaching the magic number himself, thereby forcing a contested convention in Cleveland in July.
The two men agreed to an unusual deal last week, in which Kasich pulled his campaign resources out of Indiana, where Cruz has a better chance of winning. Cruz in turn agreed not to actively campaign in New Mexico and Oregon, where Kasich seemed more likely to perform well.
But within hours of announcing the pact, there was trouble. Instead of telling his supporters in Indiana to vote for Cruz, and thereby increase Cruz's chances of beating Trump, Kasich suggested his supporters should vote for him regardless.
"I don't tell people how to vote," Kasich said. Cruz, likewise, refused to tell his supporters in Oregon and New Mexico to vote for Kasich. While Kasich and Cruz bickered, Trump attacked them both for what he called "collusion."
According to the NBC/WSJ/Marist poll, Indiana voters don't like the Cruz-Kasich deal either. Fifty-eight percent of likely GOP primary voters disapproved of the pact, and only 34 percent approved.
The poll interviewed 645 likely Republican primary voters on April 26-28. The margin of error is +/- 3.9 percentage points.
With Trump in the lead, it doesn't look as if the shaky truce will make much of a difference in Indiana. Both Trump and Cruz have stumped throughout the state for weeks, and both men plan to hold rallies in and around Indianapolis on Monday.