Users of Zyn, a brand of nicotine pouch that’s become a touchstone among right-wing commentators, extol its ability to free the mind, increase productivity, and even enhance sexual performance. “I use it every second I’m awake,” said Tucker Carlson on an episode of the Full Send comedy podcast in 2023. “Seconds before I fall asleep, I take it out.” There’s no evidence to promote Zyn as a sexual aid; nicotine actually constricts blood vessels, which can increase the risk of erectile dysfunction. The addictive substance can also raise blood sugar and blood pressure and may harden the walls of arteries,...