When does a presumptive nominee become a nominee? Here's how Donald Trump will make it official

Nearly 2,500 delegates gather in Milwaukee this week for a roll call vote to select the Republican presidential nominee, formally ending the presidential primary. Former President Donald Trump has already been the presumptive nominee for months, having clinched a majority of convention delegates on March 12, but he doesn’t officially become the party’s standard-bearer until after the roll call. While Democratic delegates are technically allowed to vote their conscience, Republican delegates remain bound to their assigned candidate no matter what. That means party rules virtually guarantee that Trump will officially become the nominee this week.