David Coonradt came to the Colorado state Republican convention as part of Ted Cruz's “persuasion team,” a squad of volunteers working to secure more delegates to propel Cruz to the party's presidential nomination. He came ready to tout the Texas senator's gun-rights and antiabortion credentials, the most crucial information he had to impart appeared on the back of his neon orange Tshirt. “The official Ted Cruz slate,” the shirt blared, with the names of 13 prospective delegates below. More than 600 people were vying Saturday for 13 delegate slots for the Republican National Convention in July. The Cruz campaign wanted...