AUDIE CORNISH, HOST:
Donald Trump looks well on his way to the Republican nomination. He's won today's Indiana primary which was a crucial test for his main rival, Ted Cruz, and others in the Republican Party hoping to stop Donald Trump. The Democratic race in Indiana is still too close to call. We're going to talk this over now with NPR senior editor and correspondent Ron Elving. Welcome to the studio, Ron.
RON ELVING, BYLINE: Hello, Audie.
CORNISH: And in Indianapolis where Ted Cruz supports have gathered is NPR's Sam Sanders. Hey there, Sam. Can you hear me?
SAM SANDERS, BYLINE: I can.
CORNISH: So Sam, this is the point in the night where people are preparing possibly to hear from the candidate right? What is going on there at the Cruz event?
SANDERS: Yeah, you know, it's sad. People are here waiting quietly. There's no sign of Cruz yet. But news began to trickle out shortly after 7 p.m., so folks knew that this had happened. But they're still waiting to hear from their guy, hopefully to hear him say that he's going to stay in this race.
CORNISH: We've heard so much about this, say, pact that Ted Cruz made with John Kasich about his deal on the campaign trail. He's really been talking big about Indiana. What went wrong?
SANDERS: I think a few things went wrong for Cruz. There was the ongoing back and forth he had with Trump. There was a failure of that Kasich pact. And some folks that I talked to who support Cruz think that Cruz let Trump kind of get to him finally. And you can see that Cruz seemed a bit rattled these last few days.
CORNISH: Right - got in his head a little bit.
CORNISH: You know, Ron, right now there are probably many conversations being had by various strategists in the Republican Party between the stop-Trump factions, pro-Trump factions coming together before the convention. Tell us what's going on.
ELVING: They are trying to decide if there is any way to deny Donald Trump a first-ballot victory. Now, it just looked just a couple of weeks ago as though not only could not it be done by June 7 or before June 7 but that...
CORNISH: Which is when the California primary is.
ELVING: And when the primaries essentially end - and not only is it now visible that you could possibly do it. It's becoming - with the possibility of a clean sweep in Indiana tonight for Donald Trump, it's becoming mathematically likely that he will get to 1,237 delegates before we get to Cleveland.
ELVING: That would mean a first-ballot victory for Donald Trump.
CORNISH: I know this can be complex as we're still working out the math. Do we know kind of what can be won in Indiana in terms of delegates?
ELVING: Yes. There are 30 delegates to be won statewide by the statewide winner. Those are Trump's. Then there are nine congressional districts, each of which has three delegates to award. And already we have seen most of those go to Donald Trump.
So we're really now just looking for three congressional districts to give us the last 12 delegates because the other 45 are all Donald Trump's. He is on his way, at least potentially and looks likely, to have that clean sweep in Indiana which is not only a mathematical boost. It's a huge psychological blow to Ted Cruz, who has put all of his hopes and all of his chips onto this state.
CORNISH: Before I let you go, Ron Elving, at the Democratic side - I know we've been saying that it's still too close to call. What does that mean? I mean, what are we actually seeing in the results that have come in?
ELVING: We have 47 percent of the vote counted thus far, and Bernie Sanders is ahead by about 10,000 votes or so. He's ahead by about 4 percentage points - in other words, 52 percent to 48 percent. It's kind of seesawed a little bit in the early counting, but this is the best lead we've seen for Bernie Sanders thus far.
But we are still looking for quite a bit of the vote to come in from Indianapolis - big city at the center of the state that does have the substantial minority population. Ditto for Gary up in the Chicago metropolitan area in the northwest part of the state. A lot of those votes have not yet come in, and that's why you're not seeing this race called even though there is a lead with 40 percent of the vote in.
So it's still possible for either candidate to win. But here's the point. It's going to come down to such a small margin. They're both going to get about the same number of delegates - about 40.
CORNISH: That's NPR's Ron Elving - thank you...
ELVING: Thank you, Audie.
CORNISH: ...And Sam Sanders in Indianapolis. Thanks so much, Sam.
SANDERS: Thanks. Transcript provided by NPR, Copyright NPR.