A report from the campaign field in Iowa demonstrates what could be a big problem for Donald Trump, getting all those people who have been showing up at his rallies to actually show up to vote: When Donald Trump held one of his boisterous rallies at the state fairgrounds this month, Bonnie and Randy Reynolds arrived two hours early to make sure they could snag seats. They bought “Make America Great Again†hats, put on campaign T-shirts and passed through a security checkpoint. The West Des Moines couple, who have two grown children, had never been to a political event...