We' ve had many important weeks in the primary voting season, but the results from the big states voting on Tuesday in the US, led by Ohio and Florida, are really, really going to be crucial.

They will give us a good idea of whether there is likely to be a contested Republication National Convention in Cleveland come July, a possibility that has lately floated into view. If Trump wins big this week, it' s a straight path to the nomination. If he doesn't, well, those in the GOP establishment that would prefer the Party to do just about anything rather than let Trump be the nominee may well get their way.

So how would it play out? In recent days, pundits have been swarming over the prospect of a contested convention, an outcome that would be, according to RealClearPolitics, ' the dream of every political junkie and the nightmare of every presidential campaign'. This guide at The Wall Street Journal provides a handy summary of what would occur. And if you don' t like the WSJ, you can find similar explainers at The Guardian, ABC News, and Mashable.com.

The trigger for a contested event would be the failure of any candidate to win 1237 delegates ahead of the Convention. If that happens, there will be run-off ballots to decide the issue. Most delegates are 'pledged' or bound to vote according to the outcome of their state' s primary in the first ballot, but there are some un-pledged delegates whose votes could get the front runner over the line in that first ballot. If not, political mayhem would break loose as growing numbers of the 2500-odd delegates become unpledged in successive ballots. This could see the front runner's advantage melt away. The outcome would be almost impossible to predict due to the myriad different arrangements the states have which bind delegates to differing degrees.

If the current process isn't confusing enough, there is also talk that an eleventh hour candidate, who has contested none of the primaries, could be parachuted in. Right now, the Republican rules dictate candidates seeking nomination at the Convention must have won a majority of delegates in at least eight states. A week before the Convention in mid-July, however, those who write the Republican rule book are due to meet. And it would be perfectly in character with the unpredictable nature of this race if they decide to change things. Certainly Mitt Romney reckons he is in with a chance. Conservative commentator Rush Limbaugh thinks Romney is on the money, saying the GOP establishment will stop at nothing to stop Trump, even if that means 'utter chaos' in Cleveland.

So how far do we have to go back to find to the last time the GOP didn't know who was going to be on its ticket by the time the National Convention rolled around?That would be 40 years ago. And you have to go back a lot further, to 1948, to find the last convention where it took multiple ballots to settle on a candidate. History fans will enjoy this recount of the contested Democratic Convention of 1924 by the New Yorker' s Amy Davidson. Back then, one delegate opined the trouble was due to the convention being held in New York, a 'wicked city'. That event went to the 103rd ballot before rejecting both front runners. You can be sure John Kasich and Marco Rubio are familiar with that piece of history.

Trump, not surprisingly, is not so keen on any scenario in which the leader in the delegate count at the end of primary voting doesn't get the prize. Late late week he told Fox News such an outcome would be 'wrong' and 'unfair'. He added that if the front runner didn't get the nomination 'there will be a lot of people (who) will be very upset...because we have really fervent, wonderful people' .

So buckle up. The wild ride looks set to continue.

Photo courtesy of Flickr user Jayel Aheram.