The Ides of March, or March 15, has long been associated with doom and destruction. In 44BC, confident populist Julius Caesar ignored a soothsayer’s warning and met his demise at the height of his adulation by an adoring public. It was also the day that Czar Nicholas II in 1917 formally abdicated his throne, and the day that Germany occupied Czechoslovakia in 1939. And now it’s the turn of the Republican Party.

This year’s Ides of March could prove pivotal for the US presidential race, as the primaries roll into five big states: Florida, Ohio, Illinois, North Carolina and Missouri. With firebrand insurgent Donald Trump still denying all the Republicans' attempts to stop him, the day’s massive delegate haul threatens to put him firmly on the path to the nomination.

Much will depend on what happens in Florida and Ohio, the home states of Florida Senator Marco Rubio and the Governor of Ohio, John Kasich. Kasich has pledged to withdraw from the contest if he loses Ohio, while Rubio has himself said that whoever wins Florida “will be the nominee of the Republican Party.” If he falls behind, he will be under enormous pressure to bow out.

This confronts Trump’s conservative rival, Ted Cruz, with a fiendish dilemma. He’s won a fair number of states, but to have a decent chance at winning the nomination, Cruz needs Kasich and especially Rubio to drop out. So Cruz wants them to do poorly. But if either or both lose their home state, it’s Trump, not Cruz, who’s most likely to grab their delegates – a hefty 99 in Florida and a chunky 66 in Ohio, all allocated on a winner-take-all basis.

On the other hand, if Rubio somehow rallies to win Florida, he’s very likely to stay in, as is Kasich if he wins Ohio. This puts Cruz and other anti-Trump forces in the awkward position of needing Rubio and Kasich both to trump Trump and to fall short.

The best outcome Cruz can hope for is for Rubio and Kasich to do just enough to win Florida and Ohio respectively, therefore denying Trump the winner-take-all delegates, but to do so badly elsewhere that they drop out anyway. Not impossible, but unlikely.

So where does that leave us?

Splitting the difference

Trump just needs to seize Ohio and Florida to put him in touching distance of the prize, but that’s a big task, especially in Ohio. Illinois and Missouri offer a combined total of 121 delegates. North Carolina’s 72 delegates are in play as well, but those are allocated on a proportional basis, so grabbing the gold isn’t quite as important there.

So if Trump picks up Florida, Ohio and does well in Illinois and/or Missouri, the fight for the Republican nomination could be all but over by Wednesday morning. But that outcome is far from pre-ordained.

Let’s say Trump loses either Ohio or (less likely) Florida, but not both. That puts his chance of clinching a majority of delegates before the convention in jeopardy, maybe Illinois and/or Missouri tipping the scale. But if he loses both Ohio and Florida, he’s extremely unlikely to win a majority of the delegates before the convention in July.

If that’s the case, anything could happen. If it is ultimately not possible to construct a winning coalition of delegates around any of the current four horsemen of the Republican Party’s political apocalypse, the party could even turn outwards, to anoint a different saviour. This would presumably be someone undamaged by the internecine warfare that would have brought the party to that impasse. That would now seem to rule out Mitt Romney, given his recent full-on personal attacks upon Donald Trump. Instead they are more likely to look to a unifier, though they would need to change the convention rules to do so.

They have called upon someone fresh in dire straits before. At the end of 2015, the party could find nobody to replace John Boehner when he suddenly stood down as speaker of the House of Representatives. Then they found someone who at first said he wasn’t interested, but later relented: Paul Ryan, Mitt Romney’s running mate in 2012.

Is this a likely outcome? Not at all. While chatter around a possible Ryan candidacy suddenly spiked as March 15 loomed, a fundraising group formed to “draft” him recently shut down after his aides disavowed its work.

It’s far more likely that Trump will emerge as the Republican nominee, followed by Cruz, then Kasich and Rubio. But if no one can garner a majority of delegates to win the first ballot at the convention, any number of scenarios could play out.

As the betting markets currently see things, by far the most electable against a Democratic opponent in the general election are John Kasich and Marco Rubio. Of these two, Kasich is rated by the markets as much more likely to win the nomination. If he scrapes a win in the Ohio primary and finally starts winning delegates, might he somehow emerge from the pack at a contested convention, perhaps with Rubio or even Cruz in tow as his running mate? We shall see.

Leighton Vaughan Williams does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Leighton Vaughan Williams, Professor of Economics and Finance and Director, Betting Research Unit & Political Forecasting Unit, Nottingham Trent University

This article was originally published on The Conversation. Read the original article.