This summer's Republican convention could be the first of its kind in more than 60 years. Donald Trump has widened his lead in the delegate count, but losing the Ohio primary makes it unclear if he can secure the 1,237 delegates required before the convention.

A contested convention for the Republicans means delegates will vote and re-vote until a nominee gets the majority. The voting process is complicated. It can involve multiple ballots, and from the start the rules are thrown out the window, reports CBS News correspondent Julianna Goldman.

John Kasich's big win in Ohio denied Trump a full victory lap. The race for delegates continues, as Republicans face the increasing odds of a contested convention.

"It's not necessarily a bad thing," RNC chairman Reince Priebus said. But he also said it may be too early to tell.

"Candidates believe that they have a pathway to getting to the majority of delegates before Cleveland. But we'll be ready for anything," Priebus said.

But sources tell CBS News that officials in the RNC, donors, and candidates Kasich and Ted Cruz are already planning for the possibility.

Traditionally, political parties have a clear nominee heading into their conventions, but this campaign has defied the rules.

At a contested convention, delegates submit ballots until someone wins a majority. There can be multiple rounds of voting.

In the first round most delegates are bound by the results of their state's primaries and caucuses. Once you get into additional rounds, delegates no longer have those obligations and could even throw their support behind someone who never officially entered the race.

Campaigns will be working behind the scenes to shift delegates' support.

"Sometimes that means candidates are jockeying for months leading into the convention," Priebues said.

The last time the Republican Party held a convention that took several ballots was in 1976.

"This is truly historic territory," political historian Terry Madonna said.

With that comes the risk of creating a deeper divide within the Republican Party.

"It's hard for me to believe that Trump supporters are just going to allow some kind of deal making to go on between the other candidates," Madonna said.

Some Republicans tell CBS News the RNC has to be planning for the real possibility that a contested convention could lead to protests, which, as we've seen, have turned violent. An estimated 50,000 people will travel to Cleveland for the GOP convention in July. The city is requesting thousands of pieces of riot gear for the four-day event.