The Republican presidential election could be headed to a contested convention—that’s when there’s no clear nominee going into the party’s July convention in Cleveland. If no one candidate wins the support of 1,237 delegates by the time the convention starts on July 18, the nomination could be up for grabs. It will be up to the delegates themselves to choose whether to nominate front-runner Donald Trump, his rivals Ted Cruz or John Kasich, or even another candidate.