At a voter meet-and-greet in Platteville, Wis., Francesca Hong, a democratic socialist who is running for the Democratic nomination for governor of Wisconsin, said that Dr. Abdul El-Sayed’s victory in Michigan offered lessons for her own campaign. “This was an example of how we are in a moment where it’s about the many and not just the money,” she said, adding: “What we can learn, too, is no complacency. We want to be ready on day one. We want to make sure that folks know what’s at stake.”