Utah is the only state in which no one can run in a partisan primary unless that candidate receives substantial support at a party endorsement meeting. An initiative is about to be launched in Utah to change that, so that anyone can gain a place on a primary ballot regardless of what happens at party meetings. Here is an op-ed by Bryan Hyde, supporting the present system.
The op-ed doesn’t address one of the strongest criticisms of the existing system, which is that some voters can’t attend a party meeting because they are temporarily away, or because they must work at the times and dates of these meetings, or because they don’t have transportation to the meetings. The same criticisms are sometimes made in Virginia, which permits any party to nominate entirely by convention instead of by primary. This year, the Virginia Republican Party nominated its statewide nominees by convention instead of by primary.