A contested American presidential nominating convention is one of those things that's taught in civics classes but never seems to actually happen.

It's the equivalent of a tie in the Electoral College that forces Congress to choose the president. Or the simultaneous and catastrophic death of most of the executive branch, thrusting the Secretary of Agriculture into the Oval Office.

There are rules for these things. In binders on a shelf somewhere. Gathering dust.

Now the speaker of the House of Representatives, himself third in the presidential line of succession, says he can no longer ignore the possibility that no Republican White House hopeful will arrive at the July convention with enough delegates to win the party's presidential nomination.

Speaker of the House Paul Ryan takes questions from reporters at a weekly news conference on Capitol Hill in Washington on Thursday. His role as chairman at the RNC won't be merely ceremonial if there's a floor fight over the presidential nomination

US Republican Presidential candidates (L-R) Donald Trump, Ted Cruz and John Kasich pose for a photo at start of the Republican Presidential Debate in Detroit on March 3

So the sort of free-for-all that we haven't seen since Gerald Ford bested Ronald Reagan in a 1976 floor fight, could turn Cleveland's Quicken Loans Arena into a historic landmark.

As if the 2016 race, with its Summer of Trump, hasn't already had enough turmoil.

Donald Trump, the GOP's billionaire front-runner, is ether comfortably on-pace to collect 1,237 convention delegates in the state-by-state primary process or woefully behind in his quest, depending on which pundit is staring down the barrel of a TV camera at any point in time.

That's been the case for weeks, even before Ohio Gov. John Kasich denied him the Buckeye State's 66 delegates with a surprise win on Tuesday.

But buzz is brewing in Washington, and Speaker Paul Ryan says he's boning up on his party's nominating convention rules.

Ryan will serve as the convention's chairman – in a normal year, a cause for photos and souvenir drink coasters.

Ryan will serve as the convention's chairman – in a normal year, a cause for photos and souvenir drink coasters

But if Trump fails to lock down the nomination before he gets to Cleveland – neither Kasich nor Texas Sen. Ted Cruz stands a chance to do it – the GOP's internal gears will start creaking and groaning.

'Nothing has changed other than the perception that this is more likely to be an open convention than we thought before,' Ryan told reporters on Thursday.

'We’re getting our minds around the idea that this could very well become a reality and that those of us who are involved in the convention need to respect that.'

Ryan said in February that his role as chairman would be 'ceremonial.' A month earlier he called the idea of a contested convention 'ridiculous.'

But on Thursday he was talking turkey about how to keep the four-day event pointed toward a practical finish line.

'My goal is to be dispassionate and to be Switzerland,' he said, invoking the ultimate D.C. metaphor for neutrality.

Ryan pledged to 'make sure the rule of law prevails and make sure that the delegates make their decision however the rules require them to do that.'

Donald Trump, the GOP's billionaire front-runner is pictured on March 5, 2016, at a news conference in West Palm Beach, Florida. He may arrive at the Cleveland convention without enough 'pledged' delegates to claim the nomination

He has been careful to point out that he has no designs on the presidency himself, even though it's possible the GOP could plug the name of anyone into the process if Trump doesn't prevail on the first ballot – even someone who didn't run in any state-level primary or caucus.

'It's not going to be me,' Ryan insisted. 'It should be someone running for president.'

Most delegates who will arrive in northeastern Ohio for the high-stakes July event are 'bound' by party rules – and, in some cases, by state laws – to initially support the candidate to whom they are assigned.

But if a first ballot doesn't produce a majority-winning victor, nearly all of them will become 'free agents.'

In some states, Trump's team has been permitted to choose the people who will attend the convention and cast those votes. Trump campaign manager Corey Lewandowski will himself be one of those delegates from his native New Hampshire.

Republican presidential candidate and Ohio governor John Kasich holds a town hall meeting Wednesday at Villanova University on the day after his win in his home state

But in most places, party bosses and grandees and elected officials are tapped to become conventioneers and told whom they must support.

Those who aren't Trump fans will break off from his camp for second or third ballots, or however many it takes to anoint a winner.

In the era before the modern primary system, this wasn't entirely rare.

President Abraham Lincoln became the Republican Party's presidential nominee in 1860, but it took three rounds of voting to get him there.

President Woodrow Wilson needed 46 convention ballots to capture the 1912 Democratic nomination. Eight years later, President Warren Harding clinched the Republican nod on the 10th ballot.

And in 1924 the Democrats put their faithful through the ordeal of 103 separate roll calls before picking John W. Davis as their nominee.

There are seemingly endless maneuvers Republican elites could employ to keep a combative Donald Trump from leading their presidential ticket.

One proposal floated Thursday morning in a hush-hush meeting of influential conservatives was encouraging Cruz and Kasich to join forces, and their delegates, in a 'unity' ticket big enough to stop Trump.

Republican U.S. presidential candidate Senator Ted Cruz is accompanied by his wife Heidi and daughter Caroline as he speaks about the primary election results in Florida, Ohio and Illinois during a campaign rally in Houston, Texas March 15, 2016

But The Donald has signaled that he intends to salt away all the delegates he needs long before the convention begins, likening his plan to a prizefighter's knockout that takes control of a match away from its referees.

That could be tough, but it's not impossible.

Trump needs to prevail in Tuesday's Arizona winner-take-all primary, and keep Cruz from winning more than 50 percent of the vote in Utah on the same day, denying the Texan a similar sweep there.

That, combined with victories in the four remaining winner-take-all states – all of which favor Trump – would put him on the right glide path.

At that point he would need to win about 43 per cent of the remaining delegates, all in states that award them proportionately, following voting percentages.

Trump has won 45 percent of the available delegates to date, doing it largely in four- and five-man contests.

With Florida Sen. Marco Rubio's exit on Tuesday night following Trump's searing victory in the Sunshine State, that task becomes easier as the pie is carved into fewer pieces.

However it turns out, Ryan – the mild-mannered Wisconsin native who was the Republican Party's vice presidential nominee in 2012 – will be in the eye of the storm come convention time.

He met Thursday night with some of the GOP's deepest-pocketed donors in swanky Palm Beach, Florida. Some were open to a Trump victory while others have spent millions to try to derail him.

Among the topics discussed, according to Politico, was the possibility of staging a convention fight.



