That idea is SO-o-o 2012. This cycle, open primaries are the key to attracting moderates, independents, and crossovers. I'm pretty sure I saw the explanation on FR.
Open primaries are a better litmus test of how well a candidate might be expected to do in a general. I’m fine with them.
They can vote for whoever they want in the general election. I don’t want them having any hand in picking the nominee. That is just crazy talk.