The Wisconsin primary could very well undo Trump's lock on the Republican nomination. Senator Ted Cruz defeated Trump in the Badger State, which will make it nearly impossible for the New York billionaire to enter the GOP convention in Cleveland with the 1,237 delegates he needs for the nomination — or even get within 100 delegates to the magic number.
But here's the catch: That doesn't mean Cruz will be the nominee.
In fact, the closer Cruz comes to catching up with Trump without actually overtaking him in the delegate count, the more likely Cruz will be denied the nomination, too, in a truly brokered convention.
First, a truly brokered — or open — convention is not really what's happening when you have one candidate very close to the needed delegate count with several others very much behind. That's simply a situation where a few deals need to be made to bring about an inevitable coronation. The best example of a convention like that was the 1976 Republican confab, where President Ford was able to use an appeal for party unity to win Ronald Reagan's support and secure the nomination. It helped that Ford had a clear lead and there was never enough rancor between the two candidates to make joining forces impossible.