Why the Republicans are likely headed for July showdown

Republican presidential candidate Ted Cruz hugs his wife, Heidi, in Milwaukee after winning the Wisconsin primary. Photo / AP

The chances of a contested Republican national convention just got higher with Donald Trump's loss to Ted Cruz in Wisconsin. How a contested convention between July 18-21 in Cleveland, Ohio, might work.

DEFINITION, PLEASE

A contested convention is when it opens without a presumptive nominee because no candidate has been able to lock up commitments from a majority of convention delegates. This year, the magic number for the Republicans is 1237 - one delegate more than half of the 2472 convention delegates.

TRUMP'S CHALLENGE

Only Trump has a potential path to lock up enough delegates before the convention, and it's an extremely slim one. To claim the nomination by the end of the primaries on June 7, he'd have to win 57 per cent of the remaining delegates. So far, he's won just 46 per cent. The delegate count so far: Trump, 743; Cruz, 517; John Kasich, 143.

The likelihood of a contested convention has increased with the Republican Party shifting away from a winner-take-all strategy, in recent years, to a more proportional way of allocating delegates. Only nine states are awarding all their GOP delegates to the winner of their primary or caucuses this year. The once-large field of GOP candidates in the 2016 race and Trump's wildcard candidacy also feed into this year's uncertainty.WHY NOW?

SIX-WEEK WINDOW

If the primary season ends with no presumptive nominee, there are still six weeks before the convention opens, during which candidates could try to cobble together a majority. If Trump is close to the magic number, for example, he might be able to scrounge up commitments from delegates in the five states and territories that didn't have statewide presidential preference votes during the primary season. He may also turn to delegates who backed candidates who have dropped out of the race, says Joshua Putnam, a political science lecturer at the University of Georgia whose frontloading.blogspot.com explores the intricacies of the primaries. "Things can happen, particularly if someone is close," says Putman. Even if a candidate can round up commitments from unbound delegates, there's really no way to know for sure how those delegates will vote.

FIRST BALLOT

When the convention opens, about 90 per cent of the delegates will be bound to a particular candidate on the first ballot, based on the results of the primaries and caucuses. If no one gets a majority of delegates on that first vote, all bets are off: Nearly three-fourths of delegates won't be bound on the second vote, and the percentage of unbound delegates keeps going up from there.

SOMEONE ELSE?

If none of the candidates can get to 1237, it's conceivable that delegates could turn to someone who didn't run in the primaries. House Speaker Paul Ryan's name keeps popping up as a possible alternative, though he's said he's not interested. Such a scenario could inflame all those voters who made their preferences known during the nominating season. Trump, for one, has talked about riots if he's denied the nomination after arriving at the convention with the biggest share of delegates, even if he's short of 1237.

RULES INTRIGUE

Each convention adopts its own rules, and those rules can have a lot to do with how the events play out. If this year's convention adopts the same rules as in 2012, a candidate would have to get support from a majority of delegates in eight states to be placed in nomination.

ABOUT LAST TIME

The last time a Republican convention opened without a clear nominee was 1976, when Gerald Ford led in delegates but lacked a majority coming into the convention. Ford beat back a challenge from Ronald Reagan and eked out the nomination on the first vote.

BROKERED CONVENTION

There's no such thing anymore, because there are no more party bosses and power brokers who can sway large chunks of delegates. You have to go back to 1952 for a true brokered convention. That's when Democrats turned to Adlai Stevenson, who won on the third ballot.

Republican presidential candidate Donald Trump addresses the crowd during a rally at Milwaukee. Photo / AP