Des Moines — Dana Van Woert strolled into this city’s downtown plaza on a September afternoon eager to help make history. Hillary Clinton was in town to headline a get-out-the-vote rally, and before it began, Van Woert scribbled her contact information on a campaign worker’s clipboard with the intention of volunteering at future events. The 27-year-old graphic designer, a graduate of Iowa State University, lives here in Des Moines and took her lunch break to cheer for a candidate who she hopes will become America’s first female president.

A few hundred feet away, just outside the event fencing, Dan Edwards was …