So how does a brokered convention work?

But will it actually happen? And who will be the nominee?

As we explained above, a brokered or contested convention means no candidate has the votes to win the party's nomination in the first round of voting by delegates. Back in the day, that meant the party bosses would wheel and deal until a candidate emerged. Now, while there's plenty of negotiating and deal-making to be had, the action to watch will be in how the actual delegates vote. Most convention delegates are bound to vote for a specific candidate in the first round of balloting (that mandate is typically based on who won their state or district). But if no candidate hits the threshold to win the nomination on the first ballot, the rules allow some of those previously "bound" delegates to vote for whomever they choose. Even more are freed if there's a third round of voting.“All of a sudden, it's going to be this question of who are the delegates, and who do they actually support, not who were they selected to support," Brown said. "That’s a very interesting question because, in a lot of states, delegates become delegates by being appointed by their party or elected by their party, not necessarily [by] being nominated by the candidate.”There are some existing rules governing who can emerge as the nominee. "Rule 40" on the Republican side, for example, includes a provision saying a candidate needs to win eight states to be eligible for the nomination. But as Brown explains, the party can change the rules essentially up until the last minute.And, on the Democratic side, superdelegates, who are not bound to vote for a specific candidate based on primary and caucus results, could offer up a candidate of their own in the first round to keep one candidate from winning the nomination outright."This is what politics is made of — there’s a reason why it's called the art of the possible," Brown said. "Politics is the only game where you play the game, you make the rules, and you adjudicate the results. You’re the player, the referee, and the governing body."Many observers — and campaigns — think the answer is yes, at least for Republicans. Both Trump and his adversaries are preparing for the possibility.And the political winds don't seem to be blowing as strongly in the front-runner's favor."The super PACs, and the other candidates, and the many Republicans out there that are basically saying we cannot allow the party to be taken over by Trump are finally having a cumulative effect," Brown said.Ted Cruz's win in Wisconsin, for example, further complicated the math for Trump. And Marco Rubio, who suspended his campaign in March, recently informed the party that he wants to hold onto the delegates he won heading into the convention, instead of releasing them to vote for Trump or another candidate. Even Republican National Committee Chairman Reince Priebus acknowledges that a contested convention could happen.“I think it’s possible and we’re preparing for that possibility,” he said on ABC News' This Week.