In the four years after the 1968 Democratic convention, the nominating power in both parties shifted from elected officials and party leaders to primary voters. For many years the effect of this change was limited, as each party continued to nominate candidates who would have been plausible under the old convention system.
But the Republican nomination of Donald Trump in 2016 illustrated a hidden weakness in the new system — the absence of peer review. It is practically impossible to imagine Trump being nominated in a system where responsible political actors had a hand in deciding who was capable of the job. CONT.
Elaine C. Kamarck, (Brookings Institution), Washington Post