Heidi M. Przybyla

USA TODAY

Republican front-runner Donald Trump holds a 15-point lead over Ted Cruz in Indiana, which holds its primary on Tuesday, according to a new NBC News/Wall Street Journal/Marist poll.

Trump leads with 49% to Cruz’s 34%, while Ohio Governor John Kasich is behind both with 13%.

The Democratic race in Indiana is closer, with Hillary Clinton holding a four-point lead over Bernie Sanders, who’s fallen far behind in the pledged delegates needed to clinch the nomination and has begun to lay off hundreds of staff.

With Trump pulling away from Cruz and Kasich in the delegate count, the two teamed up to try to deny Trump the 1,237 delegates needed to win the nomination outright, forcing a contested convention. Kasich largely ceded the state by focusing his resources in other contests on the calendar, including Oregon and Washington.

The poll found that alliance may be ineffective, with 58% of voters disapproving of the alliance. Still, 63% say it will not affect their vote.

In a general election matchup, Trump leads Clinton by 7 points in the Hoosier state while he has a single digit advantage over Democrat Bernie Sanders.

Meanwhile, another Indiana poll showed the opposite in the GOP race.

The poll from the Mike Downs Center for Indiana Politics gave Cruz a significant lead and the support of 45% of those surveyed to Trump's 29% and Kasich's 13%.

But 13% of Hoosier voters surveyed said they didn't who they would support, and the poll had a 5% margin of error, which could mean a neck-and-neck race.

"I can understand this might be an incredibly optimistic poll for Cruz," said Andy Downs, director of the politics center. "But I think there must be something going on in the electorate that makes the race closer than some people think."

Contributing: Stephanie Wang, Indianapolis Star