NEW HAMPSHIRE — The first snowstorm of the season left the roads in New Hampshire icy enough to render the 50-plus enthusiasts attending Andrew Yang's Keene town hall all the more impressive. Some three feet of snow packed on the benches in front of the Branch and Blade Brewing Company didn’t stop Yang’s fans from driving for hours to see him on a pitch-black Monday evening. Yang launched his quixotic quest for the presidency more than two years ago. At the time, he was a fairly successful but little-known entrepreneur. The New York Times described his bid, which he bolstered with the marquee issue of a universal basic income, as having a “longer-than-long” shot. As recently as this spring, Yang couldn’t crack a single percentage point in most national polling. He’s now polling around 3%,...