Rep. Beto O’Rourke, a Democrat who is running for the U.S. Senate seat held by Republican Ted Cruz, waits for his introduction at a campaign event in Dallas, Aug. 13, 2018. O’Rourke has made clear that he will not modulate his politics, betting that he can energize and activate nonvoters from past years, particularly younger ones, with left-wing authenticity and genial hustle. (Tamir Kalifa/The New York Times)