Signs the GOP Is Heading for a Showdown in Cleveland

PHOTO: Donald Trump speaks to guests during a campaign rally, March 29, 2016, in Janesville, Wisconsin. PlayScott Olson/Getty Images
WATCH Donald Trump Changes Course on Supporting GOP Nominee

Party conventions are viewed as a time for unity, an opportunity to coalesce around the party's presidential front-runner. But this year, at least on the GOP side, it looks increasingly likely that none of candidates will reach the magic number of 1,237 delegates to secure the presidential nomination. Donald Trump has to win 55 percent of the remaining delegates to get there. Ted Cruz needs to win 85 percent and John Kasich needs to win 120 percent.

By contrast, Hillary Clinton has to win just 36 percent of the remaining delegates to be eligible for the Democratic nomination.

The campaigns seemed to have accepted that Cleveland may be more of a showdown than anyone had anticipated, and are preparing accordingly.

Former Candidates Still Exerting Influence

Just because Marco Rubio suspended his campaign doesn’t mean he doesn’t matter. By ABC’s estimate, Rubio still has 171 delegates selected to vote for him at the July convention. Each state has different rules about what happens to a candidate’s delegates when they suspend their campaign. In some states, like Louisiana, Wyoming and New Hampshire, delegates become uncommitted once their original candidate drops out, meaning that they can vote for the candidate of their choice on the first round of voting at the convention. In other states, a candidate has to formally release the delegates - and Rubio has no intention of doing that. Officials from Oklahoma, Tennessee, Massachusetts, Minnesota, and Alaska all confirmed they have received a letter from Rubio stating that he would like his delegates to vote for him on the first ballot at the convention.

This has already shifted the delegate allocation in Alaska. Previously, Rubio’s delegates had been re-apportioned to Trump and Cruz, but now they will go back to Rubio.

"Of course, he's no longer a candidate [but he] wants to give voters a chance to stop Trump," Rubio spokesman Alex Burgos told ABC News.

Beefing Up Convention Staff

Tracking delegates is a complex game. Each state has different allocation rules and formulas for acquiring delegates and keeping delegates bound to candidates after they drop out. In a contested convention, where every delegate counts, keeping up with these rules, and maintaining a high level of organization, is crucial.

Trump announced on March 29 that he had hired attorney and political operative Paul J. Manafort to manage his convention strategy, and was opening an office in Washington, D.C., to coordinate with Congress and the RNC.

Manafort managed President Gerald Ford’s nomination at the 1976 convention, which was contested, and successfully staved off a challenge from Ronald Reagan.

Trump leads Cruz by over 200 delegates. The New York businessman recently tweeted that he was being treated unfairly and threatened a lawsuit over the possibility that Cruz could come out of Louisiana with more delegates by gaining the support of Rubio’s delegates.

According to the Louisiana GOP executive director, none of the Rubio delegates have officially committed to Cruz but the Trump camp is clearly gearing up for that possibility.

ABC News' Ines De La Cuetara contributed reporting.