ROBERT SIEGEL, HOST:
There's another primary election tomorrow, and this one could be the turning point in the Republican presidential race. Indiana votes, and polls there show that Donald Trump has the advantage. And if he wins, his path to the nomination will be all but undeniable. Trump's main rival, Texas Sen. Ted Cruz, is still fighting hard in the final hours before the Indiana polls open.
NPR's Don Gonyea is in South Bend, Ind., where Trump supporters are cheering their man on this evening. Don, how do things look for Trump in Indiana?
DON GONYEA, BYLINE: Things look pretty good. If you look at the polls, what was a single-digit lead in the last couple of weeks has now opened up to better than 10 points - 15 points in one poll over the weekend. Donald Trump had two huge rallies yesterday here, two more today. He's also benefited from some big non-politician endorsements - former Notre Dame head football coach Lou Holtz.
Then there's famed - or infamous, call him what you would like - former Indiana basketball coach Bobby Knight, who has kind of a Trump-like personality in and of himself. He endorsed him and did a few campaign stops with him last week. And if you listen to Trump, he is really ready to put the primaries behind him. You can hear it in his voice. Listen to him talking to reporters today at a delicatessen in Indianapolis.
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DONALD TRUMP: I would like to get on to Hillary. You know, we've beaten all of these folks, and Indiana's very important because if I win that's the end of it. In other words, we have to wait till the following week and we'll see, but I think Indiana's going to be great. We are having such popularity here, and having the endorsement of Bobby Knight and so many others has been terrific.
SIEGEL: So Trump is talking about the fall campaign against Hillary Clinton, but he still has primary rivals - Ted Cruz, for one. What are we hearing from him?
GONYEA: He's been working it. He's been working it as hard as you can work it, barnstorming the state the last couple of days. He's got a lot of help. The governor, Mike Pence, has endorsed him and has been out with him and doing events on his own. He has his new running mate, Carly Fiorina, who has been doing the same. They have all combined, Robert, by my count, 10 events today alone.
But here's the bad news for Ted Cruz - there's no evidence that it's working. He's slipping in the polls. And here's what happens when you're out there shaking hands at these small events that he's been holding, like he did today in Marion, Ind. People have real access to you. They can walk up to you. They can ask you a question.
And that's when a Trump supporter walked up to Cruz and literally got in his face. I want you to listen to this piece of tape. You'll hear this back and forth and back and forth. Give a listen.
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UNIDENTIFIED MAN: Do the math. You asked Kasich to drop out. It's your turn.
TED CRUZ: Well...
UNIDENTIFIED MAN: ...Take your own word.
CRUZ: Now I'm curious, sir...
UNIDENTIFIED MAN: Time to drop out, sir.
CRUZ: ...When Donald doesn't get the 1,237...
UNIDENTIFIED MAN: ...Donald's definitely going to get the 1,237.
GONYEA: So you can hear Cruz being calm. He never lost his cool. But we listened to maybe 12, 15 seconds there, Robert. It went on for at least five minutes. And they were arguing about Trump, talking about Trump (laughter) almost exclusively when Cruz would really like to have been talking about himself.
SIEGEL: And we heard that Trump supporter telling Ted Cruz a second ago how Donald Trump is going to get to 1,237, the number of delegates needed to clinch Republican nomination. How likely does that look right now?
GONYEA: It's looking increasingly likely, and that's why Indiana is getting so much attention. It's one of the last good-sized states to vote. It's got 57 delegates, which is a big chunk. And the goal was to deny Trump those delegates. But if he gets the bulk of them, then that puts him in a really strong position where he can actually claim the nomination before the convention this summer.
SIEGEL: That's NPR's Don Gonyea following the GOP primary campaigns in Indiana. Don, thanks.
GONYEA: Thank you. Transcript provided by NPR, Copyright NPR.