KELLY MCEVERS, HOST:

Donald Trump might have the clearest path to the Republican nomination, but if Trump doesn't reach the magic number of delegates, 1,237, then the nomination will get decided at the Republican national convention. And some in the party say that's their last chance to stop Trump.

Sasha Issenberg wrote about this strategy for Bloomberg Politics, and he says it's important to remember that the delegates who are picked in primaries and caucuses are actually people.

SASHA ISSENBERG: On these voting nights when there's a primary or caucus and we say, Ted Cruz won 10 delegates from a state, and Donald Trump won 10, and John Kasich won five, that is a number of votes that they are pledged on the first ballot from a state.

But the individual delegates - the human beings who will actually cast that ballot on the floor of the convention in Cleveland this summer - often haven't yet been picked. And so there's a kind of second shadow campaign that takes place usually within the apparatus of a state party to figure out who the individual is who will go and represent the state at the convention.

MCEVERS: Now, explain the difference between bound and unbound delegates.

ISSENBERG: A bound delegate is required to cast a ballot for a candidate based on the election results in his or her state. Most delegates - over 90 percent to the convention this summer - will be required on the first ballot of the convention to vote in accordance with how their state voted.

MCEVERS: So those 10 votes that went to Ted Cruz have to be - if they're bound, they have to vote for Ted Cruz.

ISSENBERG: That's right, on the first ballot. So if nobody gets that 1,237 number that you mentioned, then you go to a second ballot. And based on the state party rules for a given delegation, a lot of those become freed up. And so those people become free to vote. Their conscience become free to cut a deal.

MCEVERS: You write about one possibility, which is that some delegates could work as double agents. Explain that.

ISSENBERG: Yeah. So last Saturday, while everybody else was focused on Florida and Ohio, Ted Cruz was working to get delegates placed into county conventions in Iowa. Ted Cruz won the Iowa caucuses in early February and won the largest share of delegates there. But he's actually hoping to get his people placed into delegate slots that were won by Donald Trump that night. And when those people are freed after the first ballot, all of a sudden, Ted Cruz, instead of getting just over half their votes, is getting three quarters of their delegates.

MCEVERS: This all sounds kind of "House Of Cards," that you can manipulate it this much from behind the scenes.

ISSENBERG: Part of it is that the whole notion of delegates is, in a way, very abstract until you get down to the things that they actually have sort of self-determination (laughter) over at the convention. And the fact that it's a party-run event and not a public event means that a lot of the rules that we have considering things like graft and bribery don't necessarily apply.

And so I think that if we get into a situation where we are moving towards an open convention in Cleveland, there will be a lot of cutting of deals, some of them as unsavory as anything you've seen on "House Of Card," if not more so. And much of it could possibly be totally legal. It wasn't clear to me in reporting this story that it would even be illegal for a delegate to explicitly sell their vote for money.

MCEVERS: Well, let's say Donald Trump does have the most delegates going into the convention, but then, using all these tactics, the Republican national committee ultimately nominates somebody else. I mean, wouldn't that risk tearing this party apart?

ISSENBERG: Yeah. I mean, it would reaffirm everything that Trump has said about why they distrust the party establishment. I mean, it would literally be elites using their power and their access and technicalities and, at times, rewriting the rules to maintain their own power and put a favored candidate in place of the person who most likely will have come into Cleveland with not only the most delegates but an overwhelming advantage in the popular vote.

You know, Trump will have won 10, 15 million votes, and that's a lot of people to basically tell that their vote in a primary or caucus was symbolic act that got overturned because the party bosses didn't like it.

MCEVERS: That's Sasha Issenberg of Bloomberg Politics. Thank you very much.

ISSENBERG: Thank you, Kelly. Transcript provided by NPR, Copyright NPR.