Three days after the terrorist attack in which 14 people were killed at a holiday party in San Bernardino, California, a crowd of 1,500 Republican faithful streamed into the sunny lobby of Cedar Rapids' U.S. Cellular Center, passed through metal detectors, and took their seats for a four-hour oratory marathon by four presidential candidates, ostensibly focused on economic issues. But people's minds seemed elsewhere -- flags, as you drove through the city, waved at half-staff, and murmurs about homegrown terror were amplifying quickly. He wasn't in attendance that day in Iowa, and it would be two more days before he...