After Donald Trump’s defeat in Wisconsin, it seems possible that the Republican candidate for president will not emerge in the primaries. The decision will be made by delegates at the convention. Something like this has not happened in the U.S. in 64 years.

The two front-runners to win their party nomination, the Democrat and the Republican, lost yesterday in Wisconsin. Hillary Clinton was defeated by Sen. Bernie Sanders (56 percent to 43 percent), and Trump by Sen. Ted Cruz (48 percent to 35 percent). The second score is, however, more significant, because it means that the unpredictable billionaire who dominated the Republican primaries will probably not get the delegate majority (1,237) that will be necessary at the July convention in Cleveland to guarantee himself the nomination (delegates are selected in each state).

Currently, Trump has approximately 740 delegates, and Cruz approximately 520. The website FiveThirtyEight.com specializing in statistical forecasts estimates that Trump will go to the convention with approximately 1,180 delegates. If neither candidate gets the majority in Cleveland on the first ballot, then on the next ones the delegates will no longer be obliged by the results in their states and will be able to vote for whoever they want. This is what Cruz was referring to when he said on Tuesday, “Either before Cleveland, or at the convention in Cleveland, together we will win a majority of the delegates.”

The last time such an “open convention” happened in a U.S. election was in 1952. This is why just a few weeks ago it was considered a rather fictional scenario. Nobody knows how it will end. Theoretically, Trump can even bribe delegates and it will not be against the law.

Trump earned his defeat with a series of blunders. A few days ago, he posted on Twitter an ugly picture of Cruz’s wife Heidi, next to the picture of his wife Melania, who is a model, with a comment, “A picture is worth a thousand words.” Even for the low standards of the Republican campaign, in which there was talk about Trump’s penis size, it was shocking. As if it was not enough, Trump recently claimed that NATO is obsolete, that Japan and South Korea should build nuclear weapons, that abortion should be banned in the U.S., and that women who undergo this procedure should be punished. A week ago, Corey Lewandowski, Trump’s campaign manager, was briefly arrested and formally charged for battery of a journalist, whom the billionaire derided as being “hysterical and simulated.”

Republican elites have had enough of all this. During nine months of campaigning, Trump has gained so many enemies that his chances in the autumn election are minimal. The polls show that as many as two-thirds of Americans have a negative opinion about him. This is why many Republican politicians, including Mitt Romney, the party candidate in 2012, call for endorsing Cruz, who is unpopular among party members. “He [Cruz] is a Trojan horse, being used by the party bosses attempting to steal the nomination from Mr. Trump,” wrote Trump on Twitter yesterday. If, at the convention, he is eliminated in the second or subsequent ballots, even though he arrives with the highest number of delegates, he will probably run as an independent candidate, thus breaking the Republican vote and condemning them to an even more inevitable defeat than if he represented them.

Among Democrats an open convention is also possible, however much less likely. After the primaries in Wisconsin, Hillary Clinton has approximately 1,300 delegates and Sen. Sanders approximately 1,050. Moreover, the former first lady can count on the votes of nearly 500 superdelegates, party officials who go to the convention and can vote for whoever they want on the first ballot. So far, only 30 superdelegates have declared their support for Sanders, who calls himself a socialist and who only a year ago was considered a radical with no chance. After adding the superdelegates (who can change their mind), Clinton’s advantage is crushing: 1,800 to 1,080. 2,383 delegates are needed for the Democratic nomination.